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THE

PREPARATION AND MOUNTING

OP

MICROSCOPIC OBJECTS

BY

THOMAS DAVIES.

NEW YORK:
WILLIAM WOOD & CO.,

61 WALKER STREET.

K. CRAIGHEAD,

Printer, Stereotyper, and Eleetrotyper,

Caiton 93uiltiing,

81, 83, and 85 Centre Street.

V

CONTENTS.

CHAPTER I.
Apparatus 9

CHAPTER II.
To prepare and mount Objects " Dry " 21

CHAPTER III.
Mounting in Canada Balsam t 67

CHAPTER IV.
Preservative Liquids, etc., particularly where CettVare used 81

CHAPTER V.
Sections and how to cut them, with some Remarks on Dissection ... 92

CHAPTER VI.
Injection , 115

CHAPTER VII.
Miscellaneous . 131

PKEFAOB.

IN bringing this Handbook before the public, the Author
believes that he is supplying a want which has been long
felt. Much information concerning the " Preparation and
Mounting of Microscopic Objects '* has been already pub-
lished ; but mostly as supplementary chapters only, in
books written professedly upon the Microscope. From
this it is evident that it was necessary to consult a number
of works in order to obtain anything like a complete
knowledge of the subject. These pages, however, will be
found to comprise all the most approved methods of
mounting, together with the results of the Author's expe-
rience, and that of many of his friends, in every depart-
ment of microscopic manipulation ; and as it is intended
to assist the beginner as well as the advanced student,
the very rudiments of the art have not been omitted.

As there is a diversity of opinion as to the best mode
of proceeding in certain cases, numerous quotations have

VU1 PREFACE.

been made. Wherever this lias been done, the Author
believes that he has acknowledged the source from which
he has taken the information ; and he here tenders his sin-
cere thanks to those friends who so freely allowed him to
make use of their works. Should, however, any one find
his own process in these pages unacknowledged, the author
can only plead oversight, and his regret that such should
have been the case,

THE

PREPARATION AND MOUNTING

OF

MICROSCOPIC OBJECTS

CHAPTER I.

APPARATUS.

BEFORE entering into the subject of the setting of Objects for the
Microscope, the student must be convinced of the necessity of
cleanliness in everything relating to the use of that instrument.
Tn no branch is this more apparent than in the preparation of
objects; because a slide which would be considered perfectly
clean when viewed in the ordinary way is seen to be far otherwise
when magnified some hundreds of diameters ; and those constant
enemies, the floating particles of dust, are everywhere present,
and it is only by unpleasant experience that we fully learn what
cleanliness is.

Any object which is to be viewed under the microscope must,
of course, be supported in some way — this is now usually done by
placing it upon a glass slide, which on account of the transpa-
rency has a great advantage over other substances. These
*' slides " are almost always made of one size, viz., three inches
long by one broad, generally having the edges ground so as to
remove all danger of scratching or cutting any object with which
they may come in contact. The glass must be very good, else
the surface will always present the appearance of uncleanliness
and dust. This dusty look is very common amongst the cheaper

2

10 PREPARATION AND MOUNTING

kinds of slides, because they are usually " sheet " glass ; but is
seldom found in those of the quality known amongst dealers by
the name of " patent plate." This latter is more expensive at
first, but in the end there is little difference in the cost, as so many
of the cheaper slides cannot be used for delicate work if the
mounted object is to be seen in perfection. These slides vary
considerably in thickness ; care should, therefore, be taken to
sort them, so that the more delicate objects with which the higher
powers are to be used may be mounted upon the thinnest, as the
light employed in the illumination is then less interfered with.
To aid the microscopist in this work, a metal circle may be pro-
cured, having a number of different sized openings on the outer
edge, by which the glass slides can be measured. These openings
are numbered, and the slides may be separated according to these
numbers ; so that when mounting any object there will be no need
of a long search for that glass which is best suited to it.

When fresh from the dealer's hands, these slides are generally
covered with dust, &c., which may be removed by well washing
in clean rain-water ; but if the impurity is obstinate, a little wash-
ing soda may be added, care being taken, however, that every
trace of this is removed by subsequent waters, otherwise the crys-
tals will afterwards form upon the surface. A clean linen cloth
should be used to dry the slides, after which they may be laid by
for use. Immediately, however, before being used for the recep-
tion of objects by any of the following processes, all dust must be
removed by rubbing the surface with clean wash-leather or a
piece of cambric, and, if needful, breathing upon it, and then
using the leather or cambric until perfectly dry. Any small par-
ticles left upon the surface may generally be removed by blowing
gently upon it, taking care to allow no damp to remain.

We have before said, that any object to be viewed in the
microscope must have its support; but if this object is to be pre-
served, care must be taken that it is defended from the dust and
other impurities. For this purpose it is necessary to use some
transparent cover, the most usual at one time being a plate of mica,
on account of its thinness ; this substance is now, however, never
used, thin glass being substituted, which answers admirably.
Sometimes it is required to " take up " as little space as possible,

OF MICROSCOPIC OBJECTS. 11

owing to the shortness of focus of the object-glasses. It can be
procured of any thickness, from one-fiftieth to one-two-hundred-
and-fiftieth of an inch. On account of its want of strength it is
difficult to cut, as it is very liable to "fly " from the point of the
diamond. To overcome this tendency as much as possible, it
must be laid upon a thicker piece, previously made wet with
water, which causes the thin glass to adhere more firmly, and con-
sequently to bear the pressure required in cutting the covers.
The process of cutting being so difficult, especially with the thin-
ner kinds, little or nothing is gained by cutting those which can
be got from the dealers, as the loss and breakage is necessarily
greater in the hands of an amateur. It is convenient, however,
to have on hand a few larger pieces, from which unusual sizes
may be cut when required.

If the pieces required are rectangular, no other apparatus will
be required save a diamond and a flat rule ; but if circles are
wanted, a machine for that purpose should be used (of which no
description is necessary here). There are, however, other con-
trivances which answer tolerably well. One method is, to cut out
from a thick piece of cardboard a circle rather larger than the
size wanted. Dr. Carpenter recommends metal rings with a
piece of wire soldered on either side ; and this, perhaps, is the
best, as cardboard is apt to become rough at the edge when
much used. A friend of mine uses thin brass plates with circles
of various sizes " turned " through them, and a small raised han-
dle placed at one end. The diamond must be passed round the
inner edge, and so managed as to meet again in the same line,
in order that the circle may be true, after which they may be
readily disengaged. The sizes usually kept in stock by the
dealers are one-half, five-eighths, and three-quarters inch diameter ;
but other sizes may be had to order.

For the information of the beginner it may be mentioned here
that the price of the circles is a little more than of the squares ;
but this is modified in some degree by the circle being rather
lighter. If appearance, however, is cared for at all, the circles
look much neater upon the slides when not covered with the
ornamental papers ; but if these last are used (as will shortly be
described) the squares are equally serviceable.

12 PREPARATION AND MOUNTING

As before mentioned, the thin glass is made of various thick-
nesses, and the beginner will wish to know which to use. For
objects requiring no higher power than the one-inch object-glass,
the thicker kinds serve well enough ; for the half-inch the medium
thickness will be required ; while, for higher powers, the thinnest
covers must be used. The "test-objects" for the highest powers
require to be brought so near to the object-glass that they admit
of the very thinnest covering only, and are usually mounted be-
twixt glasses which a beginner would not be able to use without
frequent breakage ; but if these objects were mounted with the
common covers, they would be really worthless with the powers
which they require to show them satisfactorily.

It may be desirable to know how such small differences as
those betwixt the various thin glass covers can be measured.
For this purpose there are two or three sorts of apparatus, all,
however, depending upon the same principle. The description
of one, therefore, will be sufficient. Upon a small stand is a
short metal lever (as it may be termed) which returns by a spring
to one certain position, where it is in contact with a fixed piece
of metal. At the other end this lever is connected with a " fin-
ger," which moves round a dial like that of a watch, whereupon
are figures at fixed distances. When the lever is separated from
the metal which is stationary, the other end being connected
with the " finger " of the dial, that " finger " is moved in propor-
tion to the distance of the separation. The thin glass is, there-
fore, thrust betwixt the end of the lever and fixed metal, and each
piece is measured by the figures on the dial in stated and accu-
rate degrees. This kind of apparatus, however, is expensive, and
when not at our command, the thin glass may be placed edge-
wise in the stage forceps, and measured very accurately with the
micrometer.

Cleanliness with the thin glass is, perhaps, more necessary than
with the slides, especially when covering objects which are to be
used with a high power ; but it is far more difficult to attain, on
account of the liability to breakage. The usual method of clean-
ing these covers is as follows : — Two discs of wood, about two
inches in diameter, are procured, one side of each being perfectly
flat and covered with clean wash-leather. To the other side of

OF MICROSCOPIC OBJECTS. 13

these a small knob is firmly affixed as a handle, or where practi-
cable the whole may be made out of a solid piece. In cleaning
thin glass, it should be placed betwixt the covered sides of the
discs, and may then be safely rubbed with a sufficient pressure,
and so cleaned on both sides by the leather. If, however, the
glass be greasy, as is sometimes the case, it must be first washed
with a strong solution of potash, infusion of nut-galls, or any of
the commonly used grease-removing liquids : and with some im-
purities water, with the addition of a few drops of strong acid,
will be found very useful, but this last is not often required.

The above method of cleaning thin glass should always be
used by beginners ; but after some experience the hand becomes
so sensitive that the above apparatus is often dispensed with,
and the glasses, however thin, may be safely cleaned betwixt the
finger and thumb with a cambric handkerchief, having first
slightly damped the ends of the fingers employed to obtain firm
hold. When the dirt is very obstinate, breathing upon the glass
greatly facilitates its removal, and the sense of touch becomes so
delicate that the breakage is inconsiderable ; but this method can-
not be recommended to novices, as nothing but time spent in
delicate manipulation can give the sensitiveness required.

It was before mentioned that the ordinary glass slides were
sometimes worthless, especially for fine objects, from having a
rough surface, which presented a dusty appearance under the
microscope. This imperfection exists in some thin glass also, and
it is irremediable ; so that it is useless to attempt to cleanse it ;
nevertheless, care should be taken not to mistake dirty glass for
this roughness, lest good glass be laid aside for a fault which does
not belong to it.

When any object which it is desired to mount is of consider-
able thickness, or will not bear pressure, it is evident that a wall
must be raised around it to support the thin glass — this is usually
termed a " cell." There are various descriptions of these, accord-
ing to the class of objects they are required to protect; and
here may be given a description of those which are most gene-
rally used in mounting " dry " objects, leaving those required for
the preservation of liquids until we come to the consideration of
that mode of mounting. Many have made use of the following

14 PREPARATION AND MOUNTING

slides. Two pieces of hard wood of the usual size (3 in. by 1
in.), not exceeding one-sixteenth of an inch in thickness, are
taken, and a hole is then drilled in the middle of one of these of
the size required. The two pieces are then united by glue or
other cement, and left under pressure until thoroughly dry, when
the cell is fit for use. Others substitute cardboard for the lower
piece of wood, which is less tedious, and is strong enough for
every purpose. This class of " cell " is, of course, fitted for
opaque objects only where no light is required from below ; and
as almost all such are better seen when on a dark background,
it is usual to fix a small piece of black paper at the bottom of the
cell upon which to place them. For very small objects the
" grain " which all such paper has when magnified detracts a
little from the merit of this background ; a,nd lately I have used
a small piece of thin glass covered on the back with black var-
nish, and placed the object upon the smooth untouched side.

Another method of making these cells is as follows: — Two
"punches," similar to those used for cutting "gun-wads," are pro-
cured, of such sizes that with the smaller may be cut out the
centre of the larger, leaving a ring whose side is not less than one-
eighth of an inch wide. These rings may be readily made, the
only difficulty being to keep the sides parallel ; but a little care
will make this easy enough. For this purpose close-grained
cardboard may be conveniently used. It must have a well-glazed
surface, else the varnish or cement used in affixing the thin glass
cover sinks into the substance, and the adherence is very imper-
fect. When this takes place it is easily remedied by brushing
over the surface of the cardboard a strong solution of gum or isin-
glass ; and this application, perhaps, closes also the pores of the-
card, and so serves a double purpose. But, of course, the gum
must be perfectly dried before the ring is used.

For cardboard, gutta-percha has been substituted, but cannot
be recommended, as it always becomes brittle after a certain time,
never adheres to the glass with the required firmness, and its shape
is altered when worked with even a little heat. Leather is often
used, and is very convenient ; it should be chosen, however, of a
close texture, and free from oil, grease, and all those substances
which are laid upon it by the " dressers."

OF MICROSCOPIC OBJECTS. 15

Rings of cardboard, &c., have been rejected by persons of great
experience, because they are of such a nature that dampness can
penetrate them. This fault can be almost, if not totally, removed
by immersing them in some strong varnish, such as the asphalt
varnish hereinafter mentioned ; but they must be left long enough
when affixed to the glass slide to become perfectly dry, and this
will require a much longer time than at first would be supposed.

There has, however, been lately brought out what is termed the
ivory cell. This is a ring of ivory-like substance, which may be
easily and firmly fixed to the glass slide by any of the commonly-
used cements, and so forms a beautiful cell for any dry objects.
They are made of different sizes, and are not expensive.

Sometimes slides are used which are made by taking a thin
slip of wood of the usual size (3 in. by 1 in.), in the centre of
which is cut a circular hole large enough to receive the object. A
piece of thin glass is fixed underneath the slide, forming a cell for
the object, which may then be covered and finished like an ordi-
nary slide. This has the advantage of serving for transparent
objects for which the before-mentioned wooden slides are unsuita-
ble. A slight modification of this plan is often used where the
thickness of the objects is inconsiderable, especially with some of
the Diatomaceae, often termed "test-objects." The wooden slide
is cut with the central opening as above, and two pieces of thin
glass are laid upon it, betwixt which the diatoms or other objects
are placed, and kept in their proper position by a paper cover.
This arrangement is a good one, insomuch as the very small por-
tion of glass through which the light passes on its way to the mi-
croscope from the reflector causes the refraction or interference to
be reduced to the lowest point.

A novice would naturally think the appearance of some of the
slides above mentioned very slovenly and unfinished ; but they are
often covered with ornamental papers, which may be procured at
almost every optician's, at a cost little more than nominal, and of
innumerable patterns and colours. How to use these will be de-
scribed in another place.

It is very probable that a beginner would ask his friend what
kind of slides he would advise him to use. Almost all those made
of wood are liable to warp more or less, even when the two pieces

16 PREPARATION AND MOUNTING

are separate or of different kinds ; those of cardboard and wood
are generally free from this fault, yet the slides, being opaque, pre-
vent the employment of the Lieberkuhn. To some extent glass
slides, when covered with ornamental papers, are liable to the same
objection, as the light is partly hindered. And spmetimes the
dampness from the paste, or other substance used to affix the pa-
pers, penetrates to the object, and so spoils it, though this may be
rendered less frequent by first attaching the thin glass to the slide
by some harder cement. Much time, however, is taken up by the
labour of covering the slides, which is a matter of consideration
with some. Certainly, the cost of the glass slides was formerly
great ; but now they are reasonable enough in this respect, so that
this objection is removed. It is, therefore, well to use glass slides,
except where the thin glasses are employed for tests, &c., as above.
When the thin glass circles are placed upon the slides, and the
edge is varnished with black or coloured rings, the appearance of
finish is perfect. The trouble is much less than with most of the
other methods, and the illumination of the object very slightly in-
terfered with.

To varnish the edges of these covers, make circles of any
liquid upon the glass slide, and perform any other " circular "
work mentioned hereafter, the little instrument known as " Shad-
bolt's turntable " is almost indispensable. It is made as follows :
— At one end of a small piece of hard wood is fixed an iron
pivot about one-eighth inch thick, projecting half an inch from
the wood, which serves as a centre upon which a round brass
table three inches in diameter revolves. On the surface of this
are two springs, about one and a half inches apart, under which
the slide is forced and so kept in position, whilst the central part
is left open to be worked upon. JThe centre is marked, and two
circles half an inch and one inch in diameter are usually deeply
engraved upon the table to serve as guides in placing the slide,
that the ring may be drawn in the right position. When the
slide is placed upon the " table" underneath the springs, a camel-
hair pencil is filled with the varnish, or other medium used, and
applied to the surface of the glass ; the table is then made to
revolve, and a circle is consequently produced, the diameter of
which it is easy to regulate.

OF MICROSCOPIC OBJECTS. 17

Many objects for the microscope may be seriously injured by
allowing the fingers to touch them — many more are so minute
that they cannot be removed in this way at all, and often it is
necessary to take from a mass of small grains, as in sand, some
particular particle. To accomplish this, there are two or three
contrivances recommended : one by means of split bristles, many
of which will readily be found in any shaving brush when it has
been well used. The bristles when pressed upon any hard surface
open, and when the pressure is removed close again with a spring ;
but the use of these is limited. Camel-hair pencils are of great
service for this and many other purposes to the microscopist.
In very fine work they are sometimes* required so small that all
the hairs with the exception of one or two finer pointed ones are
removed. A few of various sizes should always be kept on hand.

Equally necessary are fine pointed needles. They are very
readily put up for use by thrusting the " eye" end into a common
penholder, so as to be firm. The points may be readily renewed,
when injured, on a common whetstone ; but when out of use
they may be protected by being thrust into a piece of cork.

Knives of various kinds are required in some branches of
microscopic work, but these will be described where " dissection,"
&c., is treated at some length, as also various forms of scissors.
In the most simple objects, however, scissors of the usual kind
are necessary. Two or three sizes should always be kept on
hand, sharp and in good order.

A set of glass tubes, kept in a case of some sort to prevent
breakage, should form part of our "fittings" and be always
cleaned immediately after use. These are generally from six to
ten inches long and from one-eighth to a quarter of an inch in
diameter. One of these should be straight and equal in width at
both ends ; one should be drawn out gradually to a fine point ;
another should be pointed as the last, but be slightly curved at
the compressed end, in order to reach points otherwise unattain-
able. It is well to have these tubes of various widths at the
points, as in some waters the finer would be inevitably stopped.
For other purposes the fine ones are very useful, especially in the
transfer of " preservative liquids," which will come under notice
in another chapter.

3*

18 PREPARATION AND MOUNTING

Forceps are required in almost all microscopic manipulations,
and consequently are scarcely ever omitted from the microscopic
box, even the most meagrely furnished ; but of these there are
various modifications, which for certain purposes are more con-
venient than the usual form. The ordinary metal ones are em-
ployed for taking up small objects, thin glass, etc. ; but when
slides are to be held over a lamp, or in any position where the
fingers cannot conveniently be used, a different instrument must
be found. Of these there are many kinds; but Mr. Page's wooden
forceps serve the purpose very well. Two pieces of elastic wood
are strongly bound together at one end, so that they may be
easily opened at the othe'r, closing again by their own elasticity.
Through the first of these pieces is loosely passed a brass stud,
resembling a small screw, and fastened in the second, and through
the second a similar stud is taken and fixed in the first — so that
on pressure of the studs the two strips of wood are opened to
admit a slide or other object required to be held in position.
The wood strips are generally used three or four inches long, one
inch wide, and about one-eighth inch thick.

Again, some objects when placed upon the glass slide are of
such an elastic nature that no cement will secure the thin glass
covering until it becomes hard. This difficulty may be overcome
by various methods. The following are as good and simple as
any. Take two pieces of wood about two inches long, three-
quarters wide, and one-quarter thick ; and a small rounded piece
one inch long and one-quarter in diameter ; place this latter be-
twixt the two larger pieces. Over one end of the two combined
pass an india-rubber band. This will give a continual pressure,
and may be opened by bringing the two pieces together at
the other end; the pressure may be readily made uniform by
paring the points at the inner sides, and may be regulated by the
strength of the india-rubber band. These bands may be made
cheaply, and of any power, by procuring a piece of india-rubber
tubing of the width required, and cutting off certain breadths.
Another very simple method of getting this pressure is mentioned
in the " Micrographic Dictionary." Two pieces of whalebone of
the length required are tied together firmly at each end. It is
evident that any object placed betwixt them will be subject to

OF MICROSCOPIC OBJECTS. 19

continual pressure. The power of this may be regulated by
the thickness and length of the whalebone. This simple con-
trivance is very useful.

Common watch-glasses should always be kept at hand. They
are certainly the cheapest, and their transparency makes them
very convenient reservoirs in which objects may be steeped in any
liquid ; as it saves much trouble to examine cursorily under the
microscope, when the air-bubbles are expelled from insects, etc.,
etc. They are readily cleaned, and serve very well as covers,
when turned upside down, to protect any objects from the dust.
For this latter purpose Dr. Carpenter recommends the use of a
number of bell-glasses, especially when one object must be left for
a time (which often happens) in order that another may be pro-
ceeded with. Wine glasses, when the " legs" are broken, may thus
be rendered very useful.

As heat is necessary in mounting many objects, a lamp will be
required. Where gas is used, the small lamp known as " Bun-
sen's" is the most convenient and inexpensive. It gives great
heat, is free from smoke, and is readily affixed to the common
gas-burner by a few feet of india-rubber tubing. The light from
these lamps is small, but this is little or no drawback to their use.
Where gas is not available, the common spirit-lamps may be used,
which are very clean and answer every purpose.

In applying the required heat to the slides, covers, &c., it is
necessary in many cases to ensure uniformity, otherwise there is
danger of the glass being broken. For this purpose a brass plate
at least three inches wide, somewhat longer, and one-eighth of
an inch thick, must be procured. It should then be affixed to a
stand, so that it may be readily moved higher or lower, in order
that the distance from the lamp may be changed at will, and
thus the degree of heat more easily regulated. This has also the
advantage of enabling the operator to allow his slides, &c., to
cool more gradually, which, in some cases, is absolutely neces-
sary,— as in fusing some of the salts, &c.

In order to get rid of air-bubbles, which are frequently dis-
agreeable enemies to the mounter of objects, an air-pump is often
very useful. This is made by covering a circular plate of metal
with a bell-glass, both of which are ground so finely at the edges

20 PREPARATION AND MOUNTING

that greasing the place of contact renders it air-tight. The pump
is then joined to the metal plate underneath, and worked with a
small handle like a common syringe. By turning a small milled
head the air may be allowed to re-enter when it is required to
remove the bell-glass and examine or perform any operation upon
the object. The mode of using this instrument will be described
hereafter, but it may be here stated that substitutes have been
devised for this useful apparatus ; but as it is now to be obtained
at a low cost, it is hardly worth while to consider them. Much
time is, in many instances, certainly saved by its use, as a very
long immersion in the liquids would be required to expel the
bubbles, where the air-pump would remove them in an hour.

The next thing to be considered is what may be termed
CEMENTS, some of which are necessary in every method of mount-
ing objects for the microscope. Of these will be given the com-
position where it is probable the young student can make use of
it ; but many of them are so universally kept as to be obtainable
almost anywhere ; and when small quantities only are required,
economy suffers more from home manufacture than from paying
the maker's profit.

Amongst these, CANADA BALSAM may, perhaps, be termed the
most necessary, as it is generally used for the preservation of
many transparent objects. It is a thick liquid resin of a light
amber colour, which on exposure to the atmosphere becomes dry
and hard even to brittleness. For this reason it is seldom used
as a cement alone where the surface of contact is small, as it
would be apt to be displaced by any sudden shock, especially
when old. In the ordinary method of using, however, it serves
the double purpose of preserving the object and fixing the thin
glass cover ; whilst the comparatively large space upon which it
lies lessens the risk of displacement. By keeping, this substance
becomes thicker ; but a very little warmth will render it liquid
enough to use even when to some extent this change has taken
place. When heated, however, for some time and allowed to
cool, it becomes hardened to any degree, which may be readily
regulated by the length of time it has been exposed, and the
amount of heat to which it has been subjected. On account of
this property it is often used with chloroform: the balsam is

OF MICROSCOPIC OBJECTS. 21

exposed to heat until, on cooling, it assumes a glassy appearance ;
it is then dissolved in pure chloroform until it becomes of the
consistence of thick varnish. This liquid is very convenient in
some cases ; as air-bubbles are much more easily got rid of than
when undiluted Canada balsam is used. _tlt also dries readily, as
the chloroform evaporates very quickly, for which reason it must
be preserved in a closely-stoppered bottle. It has been said that
this mixture becomes cloudy with long keeping, but I have not
found it so in any cases where I have used it. Should it, how-
ever, become so, a little heat will readily dispel the opacity.
The ordinary balsam, if exposed much to the air whilst being
used, becomes thicker, as has been already stated. It may be
reduced to the required consistency with common turpentine,
but I have often found this in some degree injurious to the trans-
parency of the balsam, and the amalgamation of the two is by no
means perfect. (See also Chapter III.) The cheapness of the
article renders it no extravagance to use it always undiluted;
and when preserved in a bottle with a hollow cover fitting tightly
around the neck, both surfaces being finely ground, it remains fit
for use much longer than in the ordinary jar.

ASPHALTUM. — This substance is dissolved in linseed oil, turpen-
tine, or naphtha, and is often termed " Brunswick black." It is
easily worked, but is not generally deemed a trustworthy cement,
as after a time it is readily loosened from its ground. It is, how-
ever, very useful for some purposes (such as " finishing" the
slides), as it dries quickly. I shall, however, mention a modifica-
tion of this cement a little further on.

MARINE GLUE. — No cement is more useful or trustworthy for
certain purposes than this. It is made in various proportions ;
but one really good mixture is — equal parts of india-rubber and
gum shellac ; these are dissolved in mineral naphtha with heat.
It is, however, much better to get it from the opticians or others
who keep it. It requires heat in the application, as will be explained
in Chapter IV. ; but it is soluble in few, if any, liquids used by the
microscopist, and for that reason is serviceable in the manufacture
of cells, &c. Where two pieces of glass are to be firmly cemented
together, it is almost always employed ; and in all glass troughs,
plates with ledges, &c., the beginner may find examples of its use.

22 PREPARATION AND MOUNTING

GOLD SIZE. — This substance may always be procured at any
colourman's shop. The process of its preparation is long and
tedious. It is,\herefore, not necessary to describe it here. Dr.
Carpenter says tft^t it is very durable, and may be used with
almost any preserv^ke liquids, as it is acted upon by very few
of them, turpentine being its only true solvent. If too thin, it
may be exposed for awhile to the open air, which by evaporation
gradually thickens it. Care must be taken, however, not to ren-
der it too thick, as it will then be useless. A small quantity should
be kept on hand, as it is much more adhesive when old.

LIQUID GLUE is another of these cements, which is made by
dissolving gum shellac in naphtha in such quantity that it may be
of the required consistency. This cement appears to me almost
worthless in ordinary work, as its adherence can never be relied
upon ; but it is so often used and recommended that an enumera-
tion of cements might be deemed incomplete without it. Even
when employed simply for varnishing the outside of the glass
covers, for appearance' sake alone, it invariably chips. Where,
however, oil is used as a preservative liquid, it serves very well to
attach the thin glass ; but when this is accomplished, another
varnish less liable to " chip " must always be laid upon it. (See
Chapter IV.)

BLACK JAPAN. — This is prepared from oil of turpentine, linseed
oil, amber, gum anime, and asphalt. It is troublesome to make,
and therefore it is much better to procure it at the shops. It is
a really good cement, and serves very well to make shallow cells
for liquids, as will be described in Chapter IV. The finished cell
should be exposed for a short time to the heat of what is usually
termed a " cool oven." This renders it very durable, and many
very careful manipulators make use of it for their preparations.

ELECTRICAL CEMENT. — This will be found very good for some
purposes hereinafter described. To make it melt together —

5 parts of resin.
1 " beeswax.
1 " red ochre.*

* Dr. Griffiths says that the addition of 2 parts of Canada balsam renders
this cement much more adhesive to the glass.

OF MICROSCOPIC OBJECTS. 23

It must be used whilst hot, and as long as it retains even slight
warmth can be readily moulded into any form. It is often em-
ployed in making shallow cells for liquids, as before mentioned.

GUM- WATER is an article which nobody should ever be with-
out; but labels, or indeed any substance,, affixed to glass with
common gum, are so liable to leave it spontaneously, especi-
ally when kept very dry, that I have lately added five or six drops
of glycerine to an ounce of the gum solution. This addition has
rendered it very trustworthy even on glass, and now I never use
it without. This solution cannot be kept long without undergo-
ing fermentation, to prevent which the addition of a small quan-
tity of an essential oil (as oil of cloves, &c.,) or one-fourth of its
volume of alcohol, may be made, which will not interfere in any
way with its use.

There is what is sometimes termed an extra adhesive gum-water,
which is made with the addition of isinglass, thus : — Dissolve
two drachms of isinglass in four ounces of distilled vinegar ; add
as much gum arabic as will give it the required consistency. This
will keep very well, but is apt to become thinner, when a little
more gum may be added.

All these, except one or two, are liquid, and must be kept in
stoppered bottles, or, at least, as free from the action of the air as
possible. *

When any two substances are to be united firmly, I have
termed the medium employed " a cement ;" but often the appear-
ance of the slides is thought to be improved by drawing a
coloured ring upon them, extending partly on the cover and partly
on the slide, hiding the junction of the two. The medium used
in these cases I term a VARNISH, and hereinafter mention one or
two. Of course, the tenacity is not required to be so perfect as
in the cements.

SEALING-WAX VARNISH is prepared by coarsely powdering seal-
ing-wax, and adding spirits of wine ; it is then digested at a gen-
tle heat to the required thickness. This is very frequently used
to " finish " the slides, as before mentioned, and can easily be made
of any colour by employing different kinds of sealing-wax ; but is
very liable to " chip " and leave the glass.

BLACK VARNISH is readily prepared by adding a small quantity

24 PREPARATION AND MOUNTING

of lamp-black to gold-size and mixing intimately. Dr. Carpenter
recommends this as a good finishing varnish, drying quickly and
being free from that brittleness which renders some of the others
almost worthless ; but it should not be used in the first process
when mounting objects in fluid.

Amongst these different cements and varnishes I worked a long
time without coming to any decision as to their comparative
qualities, though making innumerable experiments. The harder
kinds were continually cracking, and the softer possessed but lit-
tle adhesive power. To find hardness and adhesiveness united
was my object, and the following possesses these qualities in a
great degree : —

India-rubber J drachm.

Asphaltum 4 oz.

Mineral naphtha 10 "

Dissolve the india-rubber in the naphtha, then add the asphaltum
— if necessary heat must be employed.

This is often used by photographers as a black varnish for glass,
and never cracks, whilst it is very adhesive. Dr. Carpenter, how-
ever, states that his experience has not been favourable to it ; but
I have used it in great quantities and have never found it to leave
the glass in a single instance when used in the above proportions.
The objections to it are, however, I think easily explained, when
it is known that there are many kinds of pitch, &c., from coal,
sold by the name of asphaltum, some of which are worthless in
making a microscopic cement. When used for this purpose, the
asphaltum must be genuine and of the best quality that can be
bought. The above mixture serves a double purpose — to unite
the cell to the slide, and also as a " finishing " varnish. But it is
perhaps more convenient to have two bottles of this cement, one
of which is thicker than common varnish, to use for uniting the
cell, &c. ; the other liquid enough to flow readily, which may be
employed as a surface varnish in finishing the slides.

The brushes or camel-hair pencils should always be cleaned
after use ; but with the asphalt varnish above mentioned it is suf-
ficient to wipe off as carefully as possible the superfluous quantity
which adheres to the pencil, as, when again made use of, the var-

OF MICROSCOPIC OBJECTS. 25

irish will readily soften it ; but, of course, it will be necessary to
keep separate brushes for certain purposes.

Here it may be observed that every object should be labelled
with name and any other descriptive item as soon as mounted.
There are many little differences in the methods of doing this.
Some write with a diamond upon the slide itself; but this has the
disadvantage of being not so easily seen. For this reason a small
piece of paper is usually affixed to one end of the slide, on wrhich is
written what is required. These labels may be bought of different
colours and designs ; but the most simple are quite as good, and
very readily procured. Take a sheet of thin writing paper and
brush over one side a strong solution of gum, with the addition of
a few drops of glycerine as above recommended ; allow this to
dry, and then with a common gun-punch stamp out the circles,
which may be affixed to the slides by simply damping the gummed
surface, taking care to write the required name, etc., upon it be-
fore damping it, or else allowing it to become perfectly dry first.

There is one difficulty which a beginner often experiences in
sorting and mounting certain specimens under the microscope,
viz., the inversion of the objects ; and it is often stated to be
almost impossible to work without an erector. But this difficulty
soon vanishes, the young student becoming used to working what
at first seems in contradiction to his sight.

Let it be understood, that in giving the description of those
articles which are usually esteemed necessary in the various parts
of microscopic manipulation, I do not mean to say that without
many of these no work of any value can be done. There are, as
all will allow, certain forms of apparatus which aid the operator
considerably ; but the cost may be too great for him. A little
thought, however, will frequently overcome this difficulty, by ena-
bling him to make, or get made, for himself, at a comparatively
light expense, something which will accomplish all he desires.
As an example of this, a friend of mine made what he terms his
" universal stand," to carry various condensers, etc., etc., in the
following way : — Take a steel or brass wire, three-sixteenths or
one-quarter inch thick and six or eight inches long ; " tap" into a
solid, or make rough and fasten with melted lead into a hollow,
ball. (The foot of a cabinet or work-box answers the purpose

26 PREPARATION AND MOUNTING

very well.) In the centre of a round piece of tough board, three
inches in diameter, make a hemispherical cavity to fit half of the
ball, and bore a hole through from the middle of this cavity, to
allow the wire to pass. Take another piece of board, about four
inches in diameter, either round or square, and one-and-a-half or
two inches thick, make a similar cavity in its centre to receive the
other half of the ball, but only so deep as to allow the ball to fit
tightly when the two pieces of board are screwed together, which
last operation must be done with three or four screws. Let the
hole for the wire in the upper part be made conical (base up-
wards), and so large as only to prevent the ball from escaping
from its socket, in order that the shaft may move about as freely
as possible. Turn a cavity, or make holes, in the bottom of the
under piece, and fill with lead to give weight and steadiness.
This, painted green bronze and varnished, looks neat ; and by
having pieces of gutta-percha tubing to fit the shaft, a great vari-
ety of apparatus may be attached to it.

Again, a " condenser" is often required for the illumination of
opaque objects. My ingenious friend uses an " engraver's bottle"
(price 6d.), fills it with water, and suspends it betwixt the light
and the object. Where the light is very yellow, he tints the
water with indigo, and so removes the objectionable colour.

I merely mention these as -examples of what may be done by a
little thoughtful contrivance, and to remove the idea that nothing
is of much value save that which is the work of professional
workmen, and consequently expensive.

OF MICROSCOPIC OBJECTS. 27

CHAPTER II.

TO PREPARE AND MOUNT OBJECTS " DRY."

THE term " dry " is used when the object to be mounted is not
immersed in any liquid or medium, but preserved in its natural
state, unless it requires cleaning and drying.

I have before stated that thorough cleanliness is necessary in
the mounting of all microscopic objects. I may here add that
almost every kind of substance used by the microscopist suffers
from careless handling. Many leaves with fine hairs are robbed
of half their beauty, or the hairs, perhaps, forced into totally dif-
ferent shapes and groups ; many insects lose their scales, which
constitute their chief value to the microscopist ; even the glass
itself distinctly shows the marks of the fingers if left uncleaned.
Every object must also be thoroughly dry, otherwise dampness
will arise and become condensed in small drops upon the inner
surface of the thin glass cover. This defect is frequently met
with in slides which have been mounted quickly ; the objects not
being thoroughly dry when enclosed in the cell. Many of the
cheap slides are thus rendered worthless. Even with every care
it is not possible to get rid of this annoyance occasionally.

For the purpose of mounting opaque objects " dry," discs were
at one time very commonly made use of. These are circular
pieces of cork, leather, or other soft substance, from one-quarter
to half an inch in diameter, blackened with varnish or covered
with black paper, on which the object is fixed by gum or some
other adhesive substance. They are usually pierced longitudi-
nally by a strong pin, which serves for the forceps to lay hold of
when being placed under the microscope for examination. Some-
times objects are affixed to both sides of the disc, which is rea-
dily turned when under the object-glass. The advantage of this
method of mounting is the ease with which the disc may be

28 PREPARATION AND MOUNTING

moved, and so present every part of the object to the eye save
that by which it is fastened to the disc. On this account it is
often made use of when some particular subject is undergoing
investigation, as a number of specimens may be placed upon the
discs with very little labour, displaying all the parts. But where
exposure to the atmosphere or small particles of dust will injure
an object, no advantage which the discs may possess should be
considered, and an ordinary covered cell should be employed.
Small pill-boxes have been used, to the bottom of which a piece
of cork has been glued to afford a ground for the pin or other
mode of attachment ; but this is liable to some of the same faults
as the disc, and it would be unwise to use these for permanent
objects.

Messrs. Smith and Beck have lately invented, and are now
making, a beautiful small apparatus, by means of which the disc
supporting the object can be worked with little or no trouble into
any position that may prove most convenient, whilst a perforated
cylinder serves for the reception of the discs when out of use,
and fits into a case to protect them from dust. A pair of forceps
is made for the express purpose of removing them from the case
and placing them in the holder.

All dry objects, however, which are to be preserved should be
mounted on glass slides in one of the cells (described in Chapter
I.) best suited to them. Where the object is to be free from
pressure, care must be taken that the cell is deep enough to en-
sure this. When the depth required is but small, it is often
sufficient to omit the card, leather, or other circles, and with the
" turn-table " before described, by means of a thick varnish and
camel-hair pencil, to form a ring of the desired depth ; but
should the varnish not be of sufficient substance to give such
" walls " at once, the first application may be allowed to dry, and
a second made upon it. A number of these may be prepared at
the same time, and laid by for use. When liquids are used (see
Chapter IV.), Dr. Carpenter recommends gold-size as a good
varnish for the purpose, and this may be used in " dry" mountings
also. I have used the asphaltum and india-rubber (mentioned in
Chapter I.), and found it to be everything I could wish. The
cells, however, must be thoroughly dry, and when they will bear

OF MICROSCOPIC OBJECTS. 29

the heat they should be baked for an hour at least in a tolerably
cool oven, by which treatment the latter becomes a first-rate
medium. All dry objects which will not bear pressure must be
firmly fastened to the slide, otherwise the necessary movements
very often injure them, by destroying the fine hairs, &c. For
this purpose thin varnishes are very often used, and will serve
well enough for large objects, but many smaller ones are lost by
adopting this plan, as for a time, which may be deemed long
enough to harden the varnish, they exhibit no defect, but in a
while a " wall " of the plastic gum gathers around them, which
refracts the light, and thus leads the student to false conclusions.
In all finer work, where it is necessary to use any method of fix-
ing them to the slide, a solution of common gum, with the addi-
tion of a few drops of glycerine (Chapter I.), will be found to
serve the purpose perfectly. It must, however, be carefully filtered
through blotting paper, otherwise the minute particles in the
solution interfere with the object, giving the slide a dusty appear-
ance when under the microscope.

When mounting an object in any of these cells, the glass must
be thoroughly cleaned, which may be done with a cambric hand-
kerchief, after the washing mentioned in Chapter I. If the object
be large, the point of a fine camel-hair pencil should be dipped
into the gum solution, and a minute quantity of the liquid depo-
sited in the cell where the object is to be placed, but not to cover
a greater surface than the object will totally hide from sight.
This drop of gum must be allowed to dry, which will take a few
minutes. Breathe then upon it two or three times, holding the
slide not far from the mouth, which will render the surface adhe-
sive. Then draw a camel-hair pencil through the lips, so as to
moisten it slightly (when anything small will adhere to it quite
firmly enough), touch the object and place it upon the gum in
the desired position. This must be done immediately to ensure
perfect stability, otherwise the gum will become at least partially
dry and only retain the object imperfectly.

When, however, the objects are so minute that it would be im-
possible to deposit atoms of gum small enough for each one to
cover, a different method of proceeding must be adopted. In this
ease a small portion of the same gum solution should be placed

30 PREPARATION AND MOUNTING

upon the slide, and by means of any small instrument — a long
needle will serve the purpose very well — spread over the surface
which will be required. The quantity thus extended will be very
small, but by breathing upon it may be prevented drying whilst
being dispersed. This, like the forementioned, should be then al-
lowed to dry; and whilst the objects are being placed on the pre-
pared surface, breathing upon it as before will restore the power of
adherence.

When gum or other liquid cement has been used to fix the
objects to the glass, the thin covers must not be applied until the
slide has been thoroughly dried, and all fear of dampness arising
from the use of the solution done away with. "Warmth may be
safely applied for the purpose, as objects fastened by this method
are seldom, if ever, found to be loosened by it. As objects are
met with of every thickness, the cells will be required of different
depths. There is no difficulty in accommodating ourselves in
this — the deeper cells may be readily cut out of thick leather,
card, or other substance preferred (as mentioned in Chapter I.).
Cardboard is easily procured of almost any thickness ; but some-
times it is convenient to find a thinner substance even than this.
When thin glass is laid upon a drop of any liquid upon a slide,
every one must have observed how readily the liquid spreads be-
twixt the two : just so when any thin varnish is used to surround
an object of little substance, excessive care is needed lest the varnish
should extend betwixt the cover and slide, and so render it worth-
less. The slightest wall, however, prevents this from taking place,
so that a ring of common paper may be used, and serve a double
purpose where the objects require no deeper cell than this forms.

Many objects, however, are of such tenuity — as the leaves of
many mosses, some of the DiatomaceaB, scales of insects, &c. —
that no cell is requisite excepting that which is necessarily formed
by the medium used to attach the thin glass cover to the slide ;
and where the slide is covered by the ornamental papers mentioned
in Chapter I., and pressure does not injure the object, even this
is omitted, the thin glass being kept in position by the cover ; but
slides mounted in this manner are frequently injured by dampness,
which soon condenses upon the inner surfaces and interferes both
with the object and the clearness of its appearance.

OF MICROSCOPIC OBJECTS. 31

The thin glass, then, is to be united to the slide, so as to form
a perfect protection from dust, dampness, or other injurious mat-
ter, and yet allow a thoroughly distinct view of the object. This
is to be done by applying to the glass slide round the object some
adhesive substance, and with the forceps placing the thin glass
cover (quite dry and clean) upon it. A gentle pressure round the
edge will then ensure a perfect adhesion, and with ordinary care
there will be little or no danger of breakage. For this purpose
gold-size is frequently used. The asphalt and india-rubber varnish
also will be found both durable and serviceable. Whatever
cement may be used, it is well to allow it to become in some
measure "fixed" and dried; but where no cell or "wall" is upon
the slide, this is quite necessary, otherwise the varnish will be al-
most certain to extend, as before mentioned, and ruin the object.
It may be stated here that gold-size differs greatly in its drying
powers, according to its age, mode of preparation, &c. (Chap-
ter IV.)

Should any object be enclosed which requires to be kept flat
during the drying of the cement, it will be necessary to use some
of the contrivances mentioned in Chapter I.

When the slide is thus far advanced, there remains the " finish-
ing " only. Should the student, however, have no time to com-
plete his work at once, he may safely leave it at this stage until
he has a number of slides which he may finish at the same time.
There are different methods of doing this, some of which may be
here described.

If ornamental papers are preferred, a small circle must be cut
out from the centre a little less than the thin glass which covers
the object. Another piece of coloured paper is made of the same
size, and a similar circle taken from its centre also, or both may
be cut at the same time. The slide is then covered round the
edges with paper of any plain colour, so that it may extend about
one-eighth of an inch over the glass on every side. The orna-
mental paper is then pasted on the "object" surface of the glass,
so that the circle shows the object as nearly in the centre as pos-
sible, and covers the edges of the thin glass. The other coloured
paper is then affixed underneath with the circle coinciding with
that above. And here I may observe, that when this method is

32 PREPARATION AND MOUNTING

used there is no necessity for the edges of the slide tp bo
" ground," as all danger of scratching, &c., is done away with by
the paper cover.

Many now use paper covers, about one and a half inches long,
on the upper side\of the slide only, with the centre cut out as
before, with no otherVpurpose than that of hiding the edge of the
thin glass where it is united to the slide.

The method of " finismfig," however, which is mostly used at
the present time, is to lay a coating of varnish upon the edge of
the thin glass, and extend it some little way on the slide. When
a black circle is required, nothing serves the purpose better than
the gold-size and lampblack, or the asphalt and india-rubber var-
nish, neither of which is liable to chip ; but when used for this,
the latter should be rather thinner, as before advised. Some of
these varnishes are preferred of different colours, which may be
made by using the different kinds of sealing-wax, as described in
Chapter I. ; but they are always liable to the defects there men-
tioned. This circle cannot be made in any other way but by one
of those contrivances which have now centred in Shadbolt's turn-
table. A very little practice will enable the young student to
place his slide so that the circle may be uniform with the edge of
the thin glass.

The slide is now complete, except the addition of the name
and any other particulars which may be desirable. For this
purpose one of the methods described in Chapter I. must be
employed.

Amongst the various classes of microscopic objects now receiv-
ing general attention, the Diatomacese may be placed in a promi-
nent position. They afford endless opportunities of research,
and some very elaborate works have already been issued concern-
ing them. Professor Smith's may be mentioned as one contain-
ing, perhaps, the best illustrations. The young student may wish
to know what a diatom is. The " Micrographic Dictionary"
gives the following definition : — " A family of confervoid Algae,
of very peculiar character, consisting of microscopic brittle organ-
isms." They are now looked upon by almost all of our scientific
men as belonging to the vegetable kingdom, though some few still
assign them to the animal. They are almost invariably exceed-

OF MICROSCOPIC OBJECTS. 33

ingly small, so that the unaided eye can perceive nothing on a
prepared slide of these organisms but minute dust. Each sepa-
rate portion, which is usually seen when mounted, is termed a
" frustule," or " testule :" this consists of two similar parts, com-
posed of silica, between and sometimes around which is a mass
of viscid matter called the " endochrome." They are found in
almost every description of water, according to the variety :
some prefer sea-water, others fresh, arfcl many are seen nowhere
but in that which is a mixture of both, as the mouths of rivers, &c.
Ditches, ponds, cisterns, and indeed almost every reservoir, yield
abundance of these forms. They are not, however, confined to
" present " life ; but, owing to the almost indestructible nature of
their siliceous covering, they are found in a fossil state in certain
earths in great abundance, and are often termed " fossil Infusoria."
Upon these frustules are generally to be seen lines, or " mark-
ings," of different degrees of minuteness, the delicacy of which
often serves the purpose of testing the denning power of the
object-glasses. Some of the frustules are triangular, others cir-
cular, and, indeed, of almost every conceivable shape, many of
them presenting us with exquisitely beautiful designs.

The markings, however, are seldom seen well, if at all, until the
frustules are properly prepared, the different methods of accom-
plishing which will be given a little further on.

The collection of the fresh diatoms is so closely connected with
their preservation, that a few notes may be given upon it before
we pass on. For this purpose a number of small bottles must be
provided, which may be placed in a tin box, with a separate apart-
ment for each, so that all chance of breakage may be done away
with. The diatoms are generally of a light brown colour ; and
where they are observed in the water, the bottle may be so placed,
with the mouth closed by the finger, that when the finger is with-
drawn the water will rush in, carrying the diatoms also. If they
are seen upon plants, stones, or any other substance, they may
generally be detached and placed in the bottle. When there is
a green covering upon the surface of the water, a great quantity
of diatoms is usually found amongst it ; as also upon the surface
of the mud in those ponds where they abound. In these cases, a
broad flat spoon will be found very useful, and one is now made

3 "

34 PREPARATION AND MOUNTING

with a covering upon the broader portion of it to protect the
enclosed matter from being so readily carried off whilst bringing
it to the surface again. Where there is any depth of water, and
the spoon will not reach the surface of the mud, the bottle must
be united to a long rod, and being then carried through the upper
portion with the mouth downwards, no water will be received into
it ; but on reaching the spot required, the bottle-mouth may be
turned up, and thus become filled with what is nearest.

From the stomachs of common fish — as the cod, sole, haddock,
&c. — many specimens of Diatomacea3 may be obtained, but
especially from the crab, oyster, mussel, and other shellfish.
Professor Smith states that from these curious receptacles he has
taken some with which he has not elsewhere met. To remove
them from any of the small shell-fish, it is necessary to take the
fish or stomach from the shell, and immerse it in strong hot acid
(nitric is the best) until the^animal matter is dissolved, when the
residue must be washed and treated as^the ordinary Diatomacese
hereinafter described.

Many diatoms are seen best when mounted in a dry state, the
minute markings becoming much more indistinct if immersed in
liquid or balsam ; and for this reason those which are used as test
objects are usually mounted dry. Many kinds also are now pre-
pared in this way, as opaque objects to be examined with the
lieberkuhn, and are exquisitely beautiful. Others, however, are
almost invariably mounted in balsam ; but as these will be again
referred to in Chapter III., and require the same treatment to fit
them for the slide, it will not be out of place to describe the
cleaning and preparation of them here. As before stated, there
is much matter surrounding them which must be got rid of before
the " siliceous covering" can be shown perfectly. As, however,
we may first wish to become acquainted in some degree with what
we have to do, it is well to take a small piece of talc, and place a
few of the diatoms upon it. This may be held over the flame of
the spirit-lamp until all the surrounding matter is burnt away,
and a tolerable idea may be thus obtained as to the quality of our
treasure.

In some cases it is well to use this burning operation alone in
mounting specimens of diatoms, when they may be placed in their

OF MICROSCOPIC OBJECTS. 35

natural state upon the thin glass, burnt for awhile upon the plati-
num plate, hereafter described, and mounted dry or in balsam.

In the preparation and cleaning of Diatomacese, there is little
satisfaction unless these operations have been successfully per-
formed, as a very small portion of foreign matter seriously inter-
feres with the object. The mode of preparing them varies even
amongst the most experienced. It will be found, therefore, most
satisfactory to examine the principal of these separately, although
it may be at the risk of some little repetition.

The method which is the most frequently made use of is the
following : — Place the " gathering" containing the Diatomacese in
a small glass or porcelain vessel, add strong nitric acid, and, by the
aid of Bunsen's burner or spirit-lamp, boil for some minutes.
From time to time a drop of the mixture may be put upon a slide,
and examined under the microscope to see if all foreign matter be
got rid of. When the valves are clean, the vessel containing them
must be filled with water, and the whole left for an hour or two,
so that all the diatoms may settle perfectly. The liquid must then
be poured off carefully, or drained away by the aid of a syphon,
so that none of the diatoms are removed with it. Indeed, it is
well to examine the liquid drained off each time with the micro-
scope, as the finer forms are frequently lost in the washings. The
vessel must then be refilled with pure water, allowed to settle, and
drained as before. This washing must be repeated until a drop
being placed upon a slide and evaporated leaves no crystals.
When it is desirable to preserve the diatoms in this state before
mounting (which process will be described in another place), they
may be placed in a small phial with a little distilled water.

There are many cases in which the above method will not effect
a perfect cleansing, as certain substances with which the diatoms
are frequently mixed are not soluble in nitric acid. For this reason
the following method is resorted to : — Take a quantity of the
matter containing the Diatomacese and wash first with pure water,
to get rid of all the impurities possible. Allow this to settle per-
fectly and decant the water. Add hydrochloric acid gradually,
and when all effervescence has subsided, boil for some minutes by
aid of the lamp. When cool and the particles have subsided,
decant the hydrochloric and add nitric acid. The boiling must

36 PREPARATION AND MOUNTING

then be repeated until a drop of the liquid when placed under the
microscope shows the valves or " frustules" clean. After allowing
the diatoms to settle, the acid must be decanted, and pure water
substituted. The washing must be repeated as in the former pro-
cess until all the remains of crystals or acid are removed, when the
specimens may be preserved in small phials as stated above.

Such are the usual modes of treating the Diatomacese, but there
are certain cases in which particular methods are required to give
anything like perfect results. Persons of great experience com-
bine a variety of treatments, and thus obtain better and more uni-
form specimens. Perhaps it will be advantageous to give the
young student the process adopted by one of the most successful
preparers of these objects ; but I will first state the different me-
thods of mounting the cleaned diatoms dry: how to employ
Canada balsam and fluid in their preservation will be elsewhere
described.

It was before stated that the diatoms when cleansed might be
preserved in small phials of distilled water. When required for
mounting, shake the phial, and with a thin glass tube or rod take
up a drop of the fluid and spread it upon the surface of the slide
in the desired position. This must then be allowed to dry gra-
dually, or by the aid of the lamp if necessary, without being
shaken or interfered with, otherwise uniformity of dispersion will
be prevented. When thoroughly dry, a thin ring of one of the
adhesive varnishes — gold-size will be found as good as any — may
be drawn round the diatoms, and allowed to dry in a slight degree.
The slide and thin glass cover should then be warmed and the
latter gently pressed upon the ring of varnish until the adhesion
all round is complete.

As some of the diatoms require object-glasses of extremely
high power, and consequently short focus, to show them, they
must be as close to the outer surface of the cover as possible.
For this reason they are sometimes placed upon the under side
of the thin glass, as follows. Clean the surfaces of the slide and
cover, and with the rod or pipe place the liquid containing the
diatoms upon the thin glass, and dry as before. Trace the ring
to receive the cover upon the slide, and when almost dry, warm
both and proceed as above. Whichever of these methods is

OF MICROSCOPIC OBJECTS. 37

employed, the outer ring of coloured varnish may be applied as
elsewhere described and the slide finished.

The diatoms are also sometimes mounted betwixt two thin
glasses, as described in Chapter I., so that the light by which
they are examined may receive as little interference as possible,
and that an achromatic condenser may be brought into focus
under the slide.

Of the various modes of cleaning and mounting the Diato-
maceae, I believe that the following may be safely recommended
as affording results of the very best quality. My friend, Mr. T. G.
Rylands, gave it to me as that which he prefers, and I can safely
say that his numerous slides are at least equal to any I have ever
seen. I will give it just as I received it from him, though there
may be some little repetition of what has been said elsewhere, as
he does not appropriate any part of it as his own. He says :
In this branch of mounting, general rules alone can be laid
down, because the gatherings may contain iron, lime, fine silt,
or vegetable matter under conditions for special treatment, and
consequently the first step should be to experiment on various
kinds.

In gathering diatoms much labour is saved by judgment and
care ; hence it is desirable to get acquainted with them in their
growing condition, so that when recognised upon the sands or
other spots they may be carefully removed by the aid of the
spoon or small tin scoop before described. When growing upon
alga3 or other plants, the plants and diatoms together may be car-
ried home, in which case they must be simply drained and not
washed or pressed, in order that the diatoms be not lost. As it
is always desirable to examine the gathering on the ground, a
"Gairdner's hand microscope" with powers from 80 to 200
diameters will be found very useful. The best gatherings are
those which represent one species abundantly. Those which are
mixed may be rejected, unless they are seen to contain something
valuable or important, as the object should not be so much to
supply microscopical curiosities as to collect material which is
available for the study of nature.

The gathering when carried home should always be carefully
examined before anything is done with it ; not only on account

38 PREPARATION AND MOUNTING

of the additional information thus acquired, but also because it
often happens that a specimen should be mounted in fluid (see
Chapter IV.) in the condition in which it is gathered, as well as
cleaned and mounted in balsam (Chapter III.) and dry.

Where the gathering is taken from sand, the whole may be
shaken up in water as a preliminary operation, when much of the
sand will be separated by its own weight. The lime test, how-
ever, should be applied, viz. — a small portion of hydrochloric
acid, and if there be effervescence it must be dissolved out by
this means. From Algae and other weeds diatoms may be de-
tached by agitating the whole together in a weak solution of
nitric acid — about one of pure acid to twenty or thirty of water,
as it must be sufficiently weak to free the diatoms without des-
troying the matter to which they adhere. The diatoms may then
be separated by sifting through coarse muslin, which will retain
the Algse, &c. The process of cleaning will vary according to
circumstances. Some gatherings require to be boiled only a few
minutes in nitric acid ; but the more general plan where they are
mixed with organic or other foreign matter, is to boil them in
pure sulphuric acid until they cease to grow darker in colour
(usually from a half to one minute), and then to add, drop by drop
to avoid explosions, a cold saturated solution of chlorate of potash
until the colour is discharged, or, in case the colour does not disap-
pear, the quantity of the solution used is at least equal to that of
the acid. This operation is best performed in a wide-mouthed
ordinary beaker glass,* a test-tube being too narrow. The mix-
ture while boiling should bo poured into thirty times its bulk of
cold water, and the whole allowed to subside. The fluid must
then be carefully decanted and the vessel re-supplied once or
twice with pure water, so as to get rid of all the acid. The gather-
ing may then be transferred to a small boiling glass or test-tube,
and — the water being carefully decanted — boiled in the smallest
available quantity of nitric acid, and washed as before. This last
process has been found necessary from the frequent appearance

* These glasses are round, about six inches high, and usually contain
about eight ounces. They are rather wider at the bottom, tapering gradually
to the top, and may be generally procured at the chemists, &c.

OF MICROSCOPIC OBJECTS. 39

of minute crystals, which cannot otherwise be readily disposed of
without the loss of a considerable proportion of diatoms.

I may here mention that the washing glasses used by Mr.
Rylands are stoppered conical bottles varying in capacity from
two ounces to one quart ; the conical .form being employed to
prevent the adherence of anything to the side ; they are " stop-
pered " to render them available in the shaking process about to
be described.

The gathering, freed from acid, is now put into two inches
depth of water, shaken vigorously for a minute or two, and
allowed to subside for half an hour, after which the turbid fluid
must be carefully decanted. This operation must be repeated
until all the matter is removed which will not settle in half an
hour. The fluid removed should be examined by a drop being
put upon a slide, as in some cases very light diatoms have been
found to come off almost pure in one or more of these earlier wash-
ings. The quantity of water and time of subsidence given may be
taken generally, but may require to be modified according to cir-
cumstances and the judgment of the operator. By the repetition
and variation of this process — the shaking being the most im-
portant part — the gathering, if a pure one, will be sufficiently
clean. If, however, it contains a variety of species and forms, it
may require to be divided into different densities.

In some cases, however, it is best to divide the gathering as a
preliminary operation, which may be done by agitating it in a
quantity of water and decanting what does not readily subside.
The heavier and the lighter portions are then to be treated as two
separate boilings. But when the cleansing has been carried to
the above stage and this division is required, the plan must be
somewhat as follows : — The gathering must be shaken in a test-
tube with six inches of water, and then allowed to subside until
one inch at the top remains pure. About three inches are then
to be carefully withdrawn by a pipette, when the tube may be
filled up and the operation repeated. The three lower inches also
may then be decanted and examined. The gathering is thus
divided into three portions, viz. — that which was withdrawn by
the pipette, that which remained floating in the lower three inches
of water in the tube, and that which had settled at the bottom.

40 PREPARATION AND MOUNTING

An examination of these will inform the operator how to obtain
that particular density of gathering which he desires, and how far
it is worth while to refine this process of elutriation ; for in cases
of necessity any one, or all three, of these densities may be ope-
rated upon in the same way to separate a particular diatom.

As occasional aids, it may be remarked, that in some cases
liquor ammonice may be used in place of water, as it often sepa-
rates fine dirt, which is not otherwise easily got rid of. Some
fossil deposits require to be treated with a boiling solution of car-
bonate of soda to disintegrate them ; but this operation requires
great care, lest the alkali should destroy the diatoms. Vegetable
silicates also sometimes require to be removed by a solution of
carbonate of soda ; but as the frustules of the diatoms themselves
are but vegetable silica, even more care is required in this case.
It may be well to mention, that some diatoms are so imperfectly
siliceous that they will not bear boiling in acid at all. Some of
these may be allowed to stand in cold nitric acid some time,
whilst others of a smaller and more delicate character should,
when possible, be treated with distilled water alone.

We will now consider the mode of mounting the prepared dia-
toms, which, if used dry (as described in this chapter), should be
carefully washed two or three times with the purest distilled
water. In this branch, as in every other, each collector gives
preference to that method in which he is an adept. Thus the
diatoms may be placed on the under side of the cover, to be as
near to the object-glass as possible, or upon the slide itself; and
each plan has its advocates. Whichsoever of these is used, no-
thing seems more simple to the novice than a tolerably equal dis-
persion of the objects upon the slide or cover ; but this is by no
means so readily accomplished, consequently I give Mr. Rylands'
method, as his slides are perfect in this respect also. He always
places the diatoms upon the thin glass cover. It is not sufficient,
as is frequently thought, to take a drop of liquid containing the
cleansed material and spread it upon the cover or slide, as with-
out some additional precaution that uniform and regular distribu-
tion of the specimens is not obtained which is desirable. In order
to effect this, let a drop of the cleansed gathering be diluted suffi-
ciently for the purpose — how much must be determined in each

OF MICROSCOPIC OBJECTS. 41

case by experiment — and let the covers to be mounted be cleaned
and laid upon the brass plate. (See Chapter I.) By means of a
glass tube, about one-twelfth of an inch in diameter, stopped by
the wetted finger at the upper end, take up as much of the diluted
material as will form a moderately convex drop extending over
the whole cover. When all the covers required are thus prepared,
apply a lamp below the brass plate, and raise the temperature to
a point just short of boiling. By this means the covers will be
dried in a few minutes, and the specimens equally distributed
over the whole area. The spread of the fluid upon the covers is
facilitated by breathing upon them ; and, to insure uniformity,
care must be taken to avoid shaking them whilst drying. The
best plan is to mount at least half a dozen at once.

Before mounting, Mr. Rylands always burns the diatoms upon
the glass at a dull red heat, whether they are used with balsam or
dry. This burning, he says, is not only an additional cleaning
process, but it effectually fixes the diatoms, and prevents them
floating out if mounted with balsam. The thinnest covers may be
burnt without damage if they are placed upon a small piece of
platinum foil of the size required, which should be about one-
hundredth of an inch thick, perfectly flat, and having three of its
edges slightly bent over, so as to prevent its warping with the
heat. The small flame of a spirit-lamp, or, where there is gas, a
Bunsen's burner, may be employed. The cover should be shaded
from direct daylight, that the action of the flame may be observed
more perfectly. Care must then be taken to raise the tempera-
ture only to the dull red heat before mentioned. The cover will
then be in a fit state for mounting as required.

It has been stated in another place that it is assumed the opera-
tor is not mounting diatoms simply as microscopic objects, but as
instructive specimens. It is not, therefore, sufficient to take a
single slide as all that is required, but to have the same diatom
prepared in as many ways as possible. The following are the
principal : —

1. Mounted crude in fluid (see Chapter IV.).

2. Burnt crude upon the cover, and mounted dry or in bal-

sam (as before mentioned).

42 PREPARATION AND MOUNTING

3. Mounted dry or in balsam (see Chapter III.), after the
cleansing process already described.

I will here give Mr. Rylands' method of mounting them dry,
the fluid and balsam preparations being noticed in their respec-
tive chapters. The slide with the ring of asphalt, or black var-
nish, should have been prepared some weeks previously, in order to
allow it to dry thoroughly. When required, it must be held over
the spirit-lamp or Bunsen's burner until the ring of varnish is
softened. The burnt cover, having been heated at the same time,
must then be taken in the forceps and pressed upon the softened
varnish until it adheres all round. When cold, an outer ring of
asphalt completes the slide.

Such is the method which my friend Mr. T. G. Eylands em-
ploys in the preparation of diatoms for the microscope. I have
said enough concerning his results. It is to be feared, however,
that to some these several modes of operation may appear lengthy
and complicated ; but if read carefully, and the experiments tried,
they will be found simple enough in practice, and to occupy much
less time than an intelligible description would lead the novice to
believe necessary.

One of the most fertile as well as the most curious magazines of
Diatomaceae is guano. The siliceous forms contained therein have
been devoured by sea-birds and passed through the stomach unin-
jured, and after lying for ages may be cleaned and classified.
Many of these are not elsewhere met with, so that the student
who is desirous to enter into the study of Diatomacea3 must be in-
structed as to the best mode of obtaining them from this source.
The particulars to be observed so closely resemble those before
mentioned in the treatment of the ordinary diatoms, that it will
be sufficiently explicit to give the outlines of the process. The
guano must be first washed in pure water, allowed to subside per-
fectly, and the liquid then poured off. This must be repeated
until the top fluid is clear, and care taken not to decant the liquid
until perfect subsidence has taken place. The deposit must then
be treated with hydrochloric acid with a gentle heat for an hour
or two, adding a little fresh acid at intervals as long as it excites
any effervescence. After this nitric acid must be substituted for

OF MICROSCOPIC OBJECTS. 43

the hydrochloric, and the heat kept up to almost boiling-point for
another hour at least, adding a little fresh acid as before. When
this ceases to act, the deposit must be allowed to settle perfectly
and the acid poured off. All traces of the acid must now be
washed away with pure water, when the remains will be Diatoma-
cea3, the sand contained in the guano, and a few other forms.
Some of these may be mounted dry, as before mentioned, but the
greater portion should be put up in Canada balsam as described
in Chapter III.

Such is the ordinary method for the treatment of guano ; but
Mr. Eylands' mode of proceeding with ordinary Diatomaceaj (be-
fore given) will be found equally successful with these deposits.

The fossil Infusoria (as they were formerly called) are now
termed Diatomaeese, and are found in various parts of the world
— "Bermuda earth," "Berg-mehl" from Norway, deposit from
Mourne Mountain in Ireland, &c. They are found in immense
quantities, and afford the microscopist innumerable objects. The
same treatment as that usually employed for the Diatomacese must
be followed with these deposits, but as they are sometimes ob-
tained in hard masses, disintegration is first necessary. To effect
this, they are usually boiled for a short time in diluted liquor po-
tassce, which will soon cause the mass to fall into a mud-like de-
posit. Water must then be immediately added, in order that all
further action of the liquor potassce may be stopped, otherwise
the objects searched for will be dissolved. For this reason it is
necessary to understand what substance is being dealt with, be-
cause some deposits are much fii>er and acted upon more readily
than others.

In mounting these objects, some are so delicate that they are
almost invisible when balsam is used with them ; they are there-
fore usually mounted dry. Others, however, are much coarser,
and may be mounted in balsam like the Diatomacese mentioned
in Chapter III.

The common Infusoria cannot be mounted dry with any great
success, though a few may be placed upon the glass slide and
allowed to dry naturally, when their characters will be very well
shown. To obtain anything like a natural appearance, they must
be put up in fluid as in Chapter IV.

44 PREPARATION AND MOUNTING

Next to the Diatomacese, no class of microscopic objects has
been more looked into of late than the Foraminifera. These
animals are almost ail marine, having a jelly-like body enclosed
in one or more chambers of shell generally composed of carbonate
of lime. The shells are made with minute orifices, through which
the pseudopodia (false feet) are extended by which the animal is
enabled to lay hold of anything and draw itself along. From the
possession of these orifices they derive their name, as foramen
means a door or opening. They have been found in every depth
of sea hitherto sounded, each depth being abundant in certain
species; the lowest beds containing the greatest number of
specimens, though with less variation of kinds. In chalk
they are found in a fossil state, and may readily be shown (see
Chapter III.) ; in limestone and other hard stones they are
abundant, and some mountains are composed principally of these
shells.

The methods of obtaining Foraminifera are various. Many may
be found upon seaweeds, which should always be examined as
soon as possible after gathering. They are found in masses upon
some coasts where the waves have carried and left them ; but
they are to be found the most abundantly in sand or mud dredged
from the bottom of the sea. They must, however, be cleansed and
separated from the mass of impurity with which they are usually
mixed. This may be done in various ways, according to the
nature of the accompanying matter. If sand alone, as is frequent-
ly the case, the whole mass must be thoroughly dried, and then
stirred up in clean water. The* sand will soon subside by its own
weight, but the chambers of the Foraminifera, being filled with
air, will float upon the surface, and may be skimmed off. There
is, however, one objection to this mode of proceeding — some of
these objects are so minute, the chambers containing compara-
tively so small a quantity of air, that they sink and are cast away
with the refuse sand. On this account it is preferable to take the
trouble of searching certain soundings under the microscope, using
the camel-hair pencil, or some other contrivance before mentioned,
to extract those objects which are required. To clean the Fora-
minifera, Professor Williamson advises to transfer the specimens
to an evaporating dish containing a weak solution of caustic potash.

OF MICROSCOPIC OBJECTS. 45

This must be boiled for "some moments," when the organic
matter will be entirely dissolved, and the calcareous shells left
free from impurity. They must now be xwell washed in water, so
that all alkaline matter may be entirely got rid of.

If the specimens are in mud, we must proceed in a different
way : — Stir up the whole mass in water, and allow it to stand
until the heavier portion has sunk to the bottom ; the water may
then be poured off and examined to see if there are any objects
contained in it. This process must be repeated until the water
comes off quite clear, when (if the search is for Foraminifera only)
the solution of caustic potash may be used as before mentioned.
However the soundings, &c., are cleaned, it is necessary to assort
them under the microscope with the camel-hair pencil or other
contrivance, as it is impossible to obtain them fit for mounting
without undergoing this process.

The sea soundings taken by order of Government are drawn
from the bottom in a kind of apparatus ingeniously made for the
purpose, and the sand, mud, &c., are brought up in their original
state. Common soundings, however, are taken by lowering a
heavy piece of lead coated with tallow, which consequently brings
up a small portion of the matter from the bottom. Mr. George
Mosley, the late Secretary of the Manchester Microscopic Society,
obtained numbers of the " scrapings" from the sounding leads.
To make any use of these it is, of course, necessary to free them
from all traces of the tallow. Mr. Dancer places the sounding in
a basin and pours boiling water upon it, which causes the melted
grease to rise to the surface. When cold, this may be removed,
and the water carefully decanted. The operation may be repeated
until no grease appears, when the water may be withdrawn and
liquor ammonice used, which will form a soapy solution with any
remaining grease. This must be treated with hot water for the
final washing. Care must be taken lest the finer forms be carried
away in decanting the washing liquid. Should it be wished to
make certain as to this point, each washing should be examined
under the microscope. In some cases the process of Mr. Dancer
will prove sufficient. Mr. Dale, however, gives a method of accom-
plishing the same result, which is much more readily completed ;
and as the results cannot be found fault with, I will here give it

46 PREPARATION AND MOUNTING

in full : — It is now well known that one of the products obtained
from the naphtha of coal-tar is a volatile, oily substance, termed
benzole (or, by French chemists, benzine), whose boiling-point,
when pure, is about 1 80° Fahrenheit, which is a perfect solvent for
fatty substances. In a capsule, previously warmed on a sand-bath,
Mr. Dale mixes with the tallow soundings benzole, whose boiling-
point may be about 200°, until sufficiently diluted so as to run
freely, pressing the lumps with a glass; rod until thoroughly
mingled; the solution and its contents are then poured into a
paper filter, placed in a glass funnel ; the capsule is again washed
with benzole, until the whole of the gritty particles are removed
into the filter. A washing-bottle is then supplied with benzole,
and the contents of the filter washed to the bottom until that
liquid passes off pure, which may be tested by placing a drop
from the point of the funnel on a warm slip of glass or bright
platinum, when, if pure, the benzole will evaporate without resi-
due or tarnish ; if grease be present, the washings must be con-
tinued until they are free from it. After rinsing through weak
acid, or alcohol, for final purification, the calcareous forms will be
ready for mounting.

The filter and its contents may be left to dry spontaneously,
when the latter can be examined by the microscope. Should
time be an object, rapid drying may be effected by any of the
usual methods ; one of which, recommended by Mr.,Dale, is to
blow a stream of hot air through a glass tube held in the flame
of a Bunsen's burner. The lower the boiling-point of the benzole,
the more readily can the specimens be freed from it. A com-
moner quality may be used, but it is more difficult to dry after-
wards.

Pure benzole being costly, this may appear an expensive pro-
cess ; but, with the exception of a trifling loss by evaporation, the
whole may be recovered by simple distillation. The mixture of
tallow and benzole being placed in a retort in a hot-water, a steam,
or a sand bath, the benzole will pass into the receiver, and the
tallow or other impurities will remain in the retort. When the
whole of the benzole has distilled over, which is ascertained by
its ceasing to drop from the condenser, the heat is withdrawn and
the retort allowed to cool before the addition of fresh material.

OF MICROSCOPIC OBJECTS. 47

Half a dozen to a dozen filters, each with its specimen, can be in
process at the same time ; and the distillation of the recovered
benzole progresses as quickly as the filtration, which was practi-
cally proved on the occasion named. Great caution in the use of
benzole is to be taken in the approach of lights to the inflamma-
ble vapour.

After the Foraminifera and calcareous forms have been removed,
the residue may be treated with acids and levigation in the usual
manner, to obtain siliceous forms and discs, if there are any
present ; but to facilitate their deposition, and to avoid the loss
of any minute atoms suspended in the washings, I would suggest
the use of filtration. The conical filter is unsuitable, as the parti-
cles would spread over too great a surface of paper ; but glass
tubes open at both ends (such as broken test-tubes) will be found
to answer, the broad end covered with filtering paper, and over
that a slip of muslin tied on with a thread to facilitate the passage
of the water and prevent the risk of breaking the paper. Suspend
the tube over a suitable vessel through a hole cut in thin wood or
cardboard, pour in the washings, which can be thus filtered and
then dried. The cloth must be carefully removed, the paper cut
round the edges of the tube, and the diatoms on the paper disc
may be removed by a camel-hair pencil or otherwise, ready for
mounting. Thus many objects may be preserved which would
be either washed away or only be obtained by a more tedious
process.

Such is Mr. Dale's method of cleaning the soundings from the
tallow, and as it thoroughly accomplishes its end, and is alike
effective and not injurious to Foraminifera and diatoms, it may be
safely recommended. The weak solution of caustic potash before
advised for Foraminifera, must not be used where it is desired to
preserve the diatoms, as they would certainly be injured, or de-
stroyed altogether, if this agent were employed.

In fixing the Foraminifera upon the slide, no better plan can be
followed than the " dry cells" and gum recommended in the early
parts of this chapter. Owing to their thickness and composition,
most of them are opaque objects only ; but they are exquisitely
beautiful, and require no particular care, except in allowing the
cell, &c., to be perfectly dry, when the cover is placed upon it, or

48 PREPARATION AND MOUNTING

the damp will certainly become condensed upon the inner side,
and the examination seriously interfered with.

Many of the Foraminifera require cutting into sections if it is
wished to examine the internal structure, &c., — " decalcifying" is
also desirable in some cases; — both of these processes will be
found described at length in the chapter on Sections and Dissec-
tion.

When more than one specimen of some particular shell is ob-
tained, it is better to place them upon the slide in different posi-
tions, so as to show as much of the structure as possible. I will
conclude this subject by quoting a passage from T. Rymer
Jones : — " It is, therefore, by no means sufficient to treat these
shells as ordinary objects by simply laying them on a glass slide,
so as to see them only from one or two points of view ; they must
be carefully examined in every direction, for such is the diversity
of form that nothing short of this will be at all satisfactory. For
this purpose, they should be attached to the point of a fine needle,
so that they may be turned in any direction, and examined by
reflected light condensed upon them by means of a lens or side
reflector. In many of the thick-shelled species it will be neces-
sary to grind them down on a hone [see Chapter V.] before the
number and arrangement of the internal chambers is discernible ;
and in order to investigate satisfactorily the minutiae of their
structure, a variety of sections, made in various ways, is indispen-
sable."

Plants afford an almost inexhaustible treasury for the micro-
scope, and many of them show their beauties best when mounted
dry. When any of these also are to be mounted, care must be
taken that they are thoroughly dry, otherwise the damp will cer-
tainly arise in the cell, and injure the object ; and it may be here
mentioned that long after a leaf has every appearance of dryness,
the interior is still damp, and no way can be recommended of
getting rid of this by any quicker process than that effected by
keeping them in a warm room, as many leaves, &c., are utterly
spoiled by using a hot iron or other contrivance. The safest way
is to press them gently betwixt blotting-paper, which may be
removed and dried at short intervals ; and though this may appear
a tedious operation, it is a safe one.

OF MICROSCOPIC OBJECTS. 49

On the surface of the leaves, hairs and scales of various and
very beautiful forms are found, most of which display their beau-
ties best when removed from the leaf, and used with the polarizer.
These will be noticed in another place ; but a portion of the leaf
should always be prepared in its natural form, to show the arrange-
ment of the hair or scales upon it ; which must almost invariably
be mounted dry when used for this purpose. Many of them
require very delicate handling. The epidermis, or, as it is by some
termed, the cuticle, is the outer skin which lies upon the surface
of the leaves and other parts of most plants. This is composed
of cells closely connected, often bearing the appearance of a rude
network. In many plants, by scraping up the surface of the leaf,
a thin coating is detached, which may be torn off by taking hold
of it with the forceps. The piece may then be washed and floated
upon a glass slide, where, on drying, it will be firmly fixed, and
may usually be mounted dry. Amongst the most beautiful and
easily prepared of these may be mentioned the petal of the gera-
nium, the cells of which are well defined and amongst the most
interesting.

Closely connected with the leaves are the ANTHERS and POLLEN,
of which a great number are beautiful and interesting subjects for
the microscopist.

The mallow tribe will furnish some exquisite objects, bearing
the appearance of masses of costly jewels. These are usually
dried with pressure, but the natural form may be more accurately
preserved by allowing them to dry as they are taken from the
flower, with no interference except thoroughly protecting them
from all dust. Sometimes the anther is divided, so that the cell
required to receive them may be of as little depth as possible.
The common mallow is a beautiful object, but I think the lavatera
is a better, as it shows the pollen chambers well, when dried un-
pressed. The pollen is often set alone, and is well worth the
trouble, as it then admits of more close examination. Often it is
convenient to have the anther and pollen as seen in nature on one
slide, and the pollen alone upon another. The former should be
taken from the flowers before their full development is attained,
as if overgrown they lose much of their beauty. Some pollens
are naturally so dark that it is necessary to mount them in Canada

50 PREPARATION AND MOUNTING

balsam or fluid, as described in other places ; but they are better
mounted dry when they are not too opaque.

Here, too, we may also mention the SEEDS of many plants as
most interesting, and some of them very beautiful, objects, requir-
ing for the greater part but a low power to show them. Most of
these are to be mounted dry, as opaque objects, in cells suited to
them, but some are best seen in balsam, and will be mentioned
in Chapter III.

The CORALLINES, many of which are found on almost every
coast, afford some very valuable objects for the microscope. They
must be well washed when first procured, to get rid of all the salts
in the sea-water, dried and mounted in cells deep enough to pro-
tect them from all danger of pressure, as some of them are exceed-
ingly fragile. The white ivory appearance which some of them
present is given to them by an even covering of carbonate of lime ;
and should it be desired to examine the structure of these more
closely, it may -be accomplished by keeping them for some time
in vinegar or dilute muriatic acid, which will remove the lime and
allow of the substance being sliced in the same way as other Algae.
(" Micrographic Dictionary," p. 183.)

THE SCALES OF INSECTS. — The fine dust upon the wings of
moths and butterflies, which is readily removed when handled
carelessly, is what is generally called scales. To these the wing
owes the magnificent colours which so often are seen upon it ;
every particle being what may be termed a distinct flat feather.
How these are placed (somewhat like tiles upon a roof) may be
easily seen in the wing of any butterfly, a few being removed to
aid the investigation. The form of them is usually that of the
" battledore" with which the common game is played, but the
handle or base of the scale is often short, and the broad part varies
in proportionate length and breadth in different specimens. The
markings upon these also vary, some being mostly composed of
lines running from the base to the apex, others reminding us of
network — bead-like spots only are seen in some — indeed, almost
endless changes are found amongst them. These scales arc not
confined to butterflies and moths, nor indeed to the wings of insects.
The different gnats supply some most beautiful specimens, not
only from the wings, but also from the proboscis, &c. ; whilst

OF MICROSCOPIC OBJECTS. 51

from still more minute insects, as the podura, scales are taken
which were at one time esteemed as a most delicate test. The
gorgeous colours which the diamond beetles also show when under
the microscope are produced by light reflected from minute scales
with which the insects are covered.

In mounting these objects for the microscope it is well to have
the part of the insect from which the scales are usually taken as
a separate slide, so that the natural arrangement of them may be
seen. This is easily accomplished with the wings of butterflies,
gnats, &c. ; as they require no extraordinary care. In mounting
the scales they may be placed upon slides, by passing the wings
over the surface, or by gently scraping the wing upon the slide,
when they must be covered with the thin glass. Of course, the
extreme tenuity of these objects does away with the necessity of
any cell excepting that formed by the gold-size or other cement
used to attach the cover. The scales of the podura should be
placed upon the slide in a somewhat different manner. This insect
is without wings, and is no longer than the common flea. It is
often found amongst the sawdust in wine-cellars, continually leap-
ing about by the aid of its tail, which is bent underneath its body.
Dr. Carpenter says : — " Podurse may be obtained by sprinkling a
little oat-meal on a piece of black paper near their haunts ; and
after leaving it there for a few hours, removing it carefully to a
large glazed basin, so that, when they leap from the paper (as
they will when brought to the light), they may fall into the basin,
and may thus separate themselves from the meal. The best way
of obtaining their scales, is to confine several of them together be-
neath a wine glass inverted upon a piece of fine smooth paper ;
for the scales will become detached by their leaps against the
glass, and will fall upon the paper." These scales are removed
to the slide, and mounted as those from the gnats, &c. When
the podura has been caught without the aid of the meal, it may
be placed upon the slide, under a test-tube, or by any other mode
of confinement, and thus save the trouble of transfer from the
paper before mentioned. Another method is to seize the insect
by the leg with the forceps and drag it across the slide, when a
sufficient quantity of scales will probably be left upon it.

These scales are usually mounted "dry;" but Hogg recom-

52 PREPARATION AND MOUNTING

mends the use of Canada balsam (Chapter III.) as rendering their
structure more definite when illuminated with Wenham's para-
bolic reflector. Some advise other methods, which will be men-
tioned in Chapter IV. As most insects when undissected are
mounted in Canada balsam, the different modes of treatment
which they require will be stated in another place.

In mounting blood of any kind to show the corpuscles, or, as
they are often called, globules, which are round or oval discs, it is
but necessary to cover the slide on the spot required with a coat-
ing as thin as possible and allow it to dry before covering with
the thin glass. There is a slight contraction in the globules when
dried, but not enough to injure them for the microscope. The
shape of these varies in different classes of animals, but the size
varies much more, some being many times as large as others. —
Some of the larvce skins are beautiful objects; but, like many sec-
tions of animal and other fragile matter, are difficult to extend
upon the slide. This difficulty is easily overcome by floating the
thin object in clear water, immersing the slide and when the ob-
ject is evenly spread gently lifting it. Allow it then to dry by
slightly raising one end of the slide to aid the drainage, and cover
with the thin glass as other objects. The tails and fins of many
small fish may be mounted in a similar manner, and are well worth
the trouble.

A few objects which are best shown by mounting dry may be
here mentioned as a slight guide to the beginner, though some of
them have been before noticed ; — many of the Foraminifera as
elsewhere described. Some crystals are soluble in almost any
fluid or balsam, and should be mounted dry; a few, however,
deliquesce or effloresce, which renders them worthless as micro-
scopic objects.

The wings of butterflies and gnats, as before noticed, afford
many specimens wherewith to supply the cabinet of the young
student. A great variety also may be found amongst the ferns ;
indeed, these alone will afford the student occupation for a long
time. On the under-side of the leaves are the reservoirs for the
" spores," which in many instances somewhat resemble green vel-
vet, and are arranged in stripes, round masses, and other forms.
The spores are usually covered with a thin skin termed the indu-

OF MICROSCOPIC OBJECTS. 53

sium, which is curiously marked in some specimens, often very
like pollen-grains. The manner in which these spores with all
their accompaniments are arranged, their changes and develop-
ments afford almost endless subjects for study ; different ferns pre-
senting us with many variations in this respect totally invisible
without the aid of a microscope. The hymenophyllums (of which
two only belong to England) are particularly interesting, and the
structure of the leaves when dried makes them beautiful objects,
often requiring no balsam to aid their transparency. Portions of
the fronds of ferns should be mounted as opaque objects, after
having been dried between blotting paper, when they are not
injured by pressure; but care must be taken to .gather them at
the right time, as they do not show their beauty before they are
ripe, and if over-ripe the arrangement of the spores, &c., is altered.
The spores may be mounted as separate objects in the same man-
ner as pollen, before-mentioned, and are exquisitely beautiful
when viewed with a tolerably high power. The number of foreign
ferns now cultivated in this country has greatly widened the field
for research in this direction ; and it may also be mentioned that
the under-sides of many are found to be covered with " scales" of
very beautiful forms. A small piece of the frond of one of these
may be mounted in its natural state, but the removal of the
" scales" for examination by polarized light will be described in
another place. The mosses also are quite a little world, requiring
but a low power to show their beauties. The leaves are of various
forms, some of which resemble beautiful net-work ; the " urns" or
reservoirs for the spores, however, are perhaps the most interest-
ing parts of these objects, as also of the "liverworts" which are
closely allied to the mosses. These " urns" are generally covered
by lids, which fall off when the fruit is ripe. At this period they
are well fitted for the microscope. The common screw-moss may
be found in great abundance, and shows this denudation of the
spores very perfectly. Many of these may be easily dried without
much injury, but they should also be examined in their natural
state.

The student should not omit from his cabinet a leaf of the net-
tle and the allied foreign species, the mystery of which the micro-
scope will make plain. The hairs or stings may also be removed,

54 PREPARATION AND MOUNTING

and viewed with a higher power than when on the leaf, being so
transparent as to require no balsam, or other preservative.

There are few more interesting objects than the raphides or
plant-crystals. These are far from being rare, but in some plants
they are very minute, and consequently require care in the mount-
ing, as well as a high magnifying power to render them visible ;
in others they are so large that about twenty-five of them placed
point to point would reach one inch. Some of these crystals are
long and comparatively very thin, which suggested the name
(rapkis, a needle) ; others are star-like, with long and slender
rays ; while others again are of a somewhat similar form, each ray
being solid and short. If the stem of rhubarb, or almost any of
the hyacinth tribe, be bruised, so that the "juice" may flow
upon the slide, in all probability some of these crystals will be
found in the fluid. To obtain them clean, they must be freed
from all vegetable matter by maceration. After this they must
be thoroughly washed and mounted " dry." They are also good
polarizing objects, giving brilliant colours; but when used for
this purpose they must be mounted as described in Chapter III.
A few plants which contain them may be mentioned here. The
Cactacese are very prolific ; the orchids, geraniums, tulips, and the
outer coating of the onion, furnish the more unusual forms.

The Fungi are generally looked upon as a very difficult class of
objects to deal with, but amongst them some of the most availa-
ble may be found. The forms of many are very beautiful, but are
so minute as to require a high magnifying power to show them.
The mould which forms on many substances is a fungus, and in
some cases may be dried and preserved in its natural state. A
friend of mine brought me a rose-bush completely covered with a
white blight. This was found to be a fungus, which required a
high magnifying power to show it. Being a very interesting ob-
ject, it was desirable to preserve it, and this was perfectly effected
without injury to the form by simply drying the leaf in a room
usually occupied. Amongst the fungi are many objects well
worth looking for, one of which is the Diachcea elegans. This,
the only species, says the " Micrographic Dictionary," is found in
England upon the living leaves of the lily-of-the-valley, &c. These
little plants grow in masses, reminding one of mould, to a height

OF MICROSCOPIC OBJECTS. 55

of a quarter of an inch, and each "stem" is covered with a
sheath, in shape somewhat like an elongated thimble. When ripe,
the sheath falls off and reveals the same shaped column, made up
of beautifully fine net-work, with the spores lying here and there.
This dries well, and is a good object for the middle powers.
Amongst the fungi the blights of wheat and of other articles of
food may be included. Many of them may be mounted " dry ;"
others, however, cannot be well preserved except in liquids, and
will be referred to in Chapter IV. Amongst the zoophytes and
sea-mats, commonly called " sea-weeds," may be found many very
interesting objects to be mounted " dry." When this mode of
preservation is used, it is necessary that all the searsalt be
thoroughly washed from them. As they are, however, most fre-
quently mounted in balsam or liquid, they will be more fully
noticed in other places.

The scales of fishes are generally mounted " dry " when used as
ordinary objects ; but for polarized light, balsam or liquid must
be used, as noticed in Chapter III. The variety and beauty of
these are quite surprising to the novice. It is also very interest-
ing to procure the skin of the fish when possible, and mount it
on a separate slide to show how the scales are arranged. The
sole is one of the most unusual forms, the projecting end of each
scale being covered with spines, which radiate from a common
centre, while those at the extremity are carried out somewhat
resembling the rays of a star. One of the skates has a spine pro-
jecting from the centre of each scale, which is a very curious
opaque object, especially when the skin is mounted in the manner
described. The perch, roach, minnow, and others of the common
fishes give the student good objects for his cabinet, and may be
procured without difficulty.

Insects which are very transparent, or have the " metallic lustre"
with which any medium would interfere, are mounted " dry."
The diamond-beetle, before mentioned, is a splendid example of
this ; the back is generally used, but the legs, showing the curious
feet, are very interesting objects. Indeed, amongst the legs and
feet of insects there is a wide field of interest. When they are
of a " horny " nature, it is best to dry them in any form prefer-
red, but to use no pressure ; when, however, they are wanted flat,

56 PREPARATION AND MOUNTING

so as to show the feet, &c., extended, they must be dried with a
gentle pressure betwixt blotting-paper if possible. But this will
be treated more fully in Chapter III.

The eyes of insects are sometimes allowed to dry in their natural
shape, and mounted as opaque objects ; but generally they are
used as transparencies in balsam or liquid, so the description of
the treatment which they require will be deferred to Chapter III.

Hairs, when not too dark, are sometimes transparent enough
when mounted dry, but are usually mounted in balsam. These
also will be more fully noticed in another place.

These are a few of the objects which are often mounted dry, but
some of them should be shown in balsam or liquid also, and there
is much difference of opinion as to the best way of preserving
others. This, however, is explained by the transparency which
the balsam gives interfering with one property of the object and
yet developing another which would have remained invisible if
preserved dry. The only method of overcoming this difficulty is
to keep the object mounted in both ways, which is comparatively
little trouble.

I may here mention that many prefer the lieberkuhn for the
illumination of opaque objects ; and a good back-ground is gained
by putting upon the under side of the slide, immediately beneath
the object, a spot of black varnish, which does not interfere
materially with the light.

OF MICROSCOPIC OBJECTS. 5 7

CHAPTER III.

MOUNTING IN CANADA BALSAM.

THE nature and use of tliis substance has been before spoken, of,
so the method of working with it may be at once described.

Perfect dryness of the objects is, if possible, more necessary in
this mode of mounting than any other, as dampness remaining in
the object will assuredly cause a cloudiness to make its appear-
ance in a short time after it is fixed. Where pressure does not
injure the specimens, they are most successfully treated when first
dried betwixt the leaves of a book, or in any other way which may
prove most convenient, as noticed in Chapter II.

Before describing the methods of proceeding with any particu-
lar objects, general rules may be given which should be observed
in order to succeed in this branch of mounting,

As the object is to be thoroughly immersed in the balsam, it is
evident that when it has once been covered, so it must remain,
unless we again free it by a process hereafter mentioned, which is
very troublesome ; and on this account there must be nothing
whatever in the balsam except the object. The inexperienced
may think this an unnecessary caution ; but the greatest difficulty
he will meet with is to get rid of minute bubbles of air, perhaps
invisible to the naked eye, which appear like small globules when
under the microscope, and render the slide unsightly, or even
worthless. Ten objects out of eleven contain air, or at least are
full of minute holes which are necessarily filled with it ; so that
if they should be immersed in any liquid of thick consistency,
these cells of air would be imprisoned, and become bubbles. The
air, then, must be got rid of, and this is usually accomplished by
soaking for some time in turpentine, the period required differing
according to the nature of the object. In some cases, the turpen-
tine acts upon the colour, or even removes it altogether, so that it

4

58 PREPARATION AND MOUNTING

must be watched carefully. Often, however, this is an advantage,
as where the structure alone is wanted, the removal of the colour-
ing matter renders it more transparent. There are objects, how-
ever, which retain the air with such tenacity that soaking alone
will not remove it. If these will bear heat without being injured,
they may be boiled in turpentine, or even in balsam, when the air
will be partly or totally expelled. But where heat is objection-
able, they must be immersed in the turpentine, and so submitted
to the action of the air-pump. Even with this aid, sometimes
days are required to accomplish it perfectly, during which time
the air should be exhausted at intervals of five or six hours, if con-
venient, and the objects turned over now and then.

Sometimes the objects are so minute that it is impossible to sub-
mit them to any soaking, and in this case they must be laid upon
the slide at once, and the turpentine applied to them there. But
it must not be forgotten that there are some few which are much
better mounted in such a way that the balsam may thoroughly
surround, and yet not penetrate, the substance more than necessary.
Sections of teeth are amongst these, which will be noticed in
another place, and some insects (see Dr. Carpenter) when required
to show the " ramifications of the trachea?."

Having freed the object, then, from these two enemies — damp-
ness and air — we must proceed to mount it.

The slide must first be cleaned ; then on the centre a quantity
of balsam must be placed with a bluntly-pointed glass rod, accord-
ing to the size of the object about to be mounted. To this a
slight heat must be applied, which will cause any bubbles to rise
from the surface of the slide, so that they may be readily removed
with a needle. The object should be freed from all air by steep-
ing in turpentine, as before described, and then from superfluous
liquid by a short drainage, and carefully laid upon, or where it is
practicable thrust into, the balsam, prepared on the slide as above.
In the former case, or where the balsam has not totally covered
the object, a small quantity must be taken, warmed, and dropped
upon it, and any bubbles removed by the needle as before. To
cover this, the thin glass must be warmed, and beginning at one
side, allowed to fall upon the balsam, driving a small " wave" be-
fore it, and thus expelling any bubbles which may remain. This

OF MICROSCOPIC OBJECTS. 59

is quite as safely performed (if not more so) by making a solution
of balsam in turpentine of the consistency of thick varnish. The
thin glass cover may be slightly coated with this, and will then be
much less liable to imprison any air, which frequently happens
when the cover is dry. Bubbles, however, will sometimes make
their appearance in spite of all care ; but when the object is com-
paratively strong, they may be removed by keeping the slide ra-
ther warm, and working the cover a little, so as to press them to
one side, when they should be immediately removed with a needle
point, otherwise they are again drawn under.

Where the slide requires keeping warm for any length of time,
a hot-water bath is sometimes made use of, which is simply a flat
tin, or other metal case, with a mouth at the side, that when the
hot water is introduced it may be closed up, and so retain its
warmth for a long time. In working, the slide is laid upon it,
and so admits of longer operations, when required, without grow-
ing cold. Sometimes a spirit-lamp is placed under it to keep up
an equal heat through excessively long processes. Where the
time required, however, is but short, a thick brass plate is some-
times used (see Chapter I.), which is heated to any degree that
is required, and the slide placed upon it.

Some objects, which -are so thin that they are usually floated
upon the slide, as before stated, require no steeping in turpentine
or other liquid. These are best mounted by covering with a lit-
tle diluted balsam, and after this has had time to penetrate the
substance, ordinary balsam is laid upon it, and the slide finished
in the usual manner.

I have stated that the balsam is usually applied to the slide and
objects with a " bluntly-pointed glass rod ;" but for the purpose of
drawing the balsam from the bottle, and conveying it to the de-
sired place, Dr. Carpenter uses a glass syringe with a free opening.
These are his instructions : — " This (the syringe) is most readily
filled with balsam, in the first instance, by drawing out the pis-
ton, and pouring in balsam previously rendered more liquid by
gentb warmth ; and nothing else is required to enable the opera-
tor at any time to expel precisely the amount of balsam he may
require, than to warm the point of the syringe, if the balsam
should have hardened in it, and to apply a very gentle heat to the

60 PREPARATION AND MOUNTING

syringe generally, if the piston should not then be readily pressed
down. When a number of balsam objects are being mounted at
one time, the advantage of this plan in regard to facility and
cleanliness (no superfluous balsam being deposited on the slide)
will make itself sensibly felt."

When the "mounting" is thus far accomplished, the outer
" wall " of balsam may be roughly removed after a few hours have
elapsed ; but great care is necessary lest the cover be moved or
interfered with in any way. In this state it may be left for the
final cleansing until the balsam becomes hard, which takes place
sooner or later, according to the degree of warmth it has been
subjected to. A mantel-piece, or some place about equal to it in
temperature, is the best suited to this purpose ; and when the
requisite hardness is attained, it may be proceeded with as follows :
— With a pointed knife the balsam must be scraped away, taking
care that the thin glass be not cracked by the point getting under
it. If used carefully, the knife will render the slide almost clean ;
but any minute portions which still adhere to the' glass must be
rubbed with linen dipped in turpentine or spirit. If the balsam
is not very hard, these small fragments are readily removed by
folding a piece of paper tightly in a triangular form with many folds,
and damping the point with which the glass is rubbed. As the
paper becomes worn with the friction, the balsam will be carried
off' with it. In some cases I have found this simple expedient
very useful.

Sometimes the object to be mounted is of such a thickness as
to require a cell. For this purpose glass rings are used (as de-
scribed in Chapter IV.), and filled with balsam. The best mode
of doing this is thus described by Mr. T. S. Ralph in the Micro-
scopic Journal: — "The question was asked me when I was in
England, if I knew how to fill a cell with Canada balsam and
leave behind no air-bubbles ? I replied in the negative ; but now
I can state how to accomplish this. Fill the cell with clear spirit
of turpentine, place the specimen in it, have ready some balsam
just fluid enough to flow out of the bottle when warmed by the
hand ; pour this on the object at one end, and, gradually inclin-
ing the slide, allow the spirit of turpentine to flow out on the
opposite side of the cell till it is full of balsam ; then take up the

OF MICROSCOPIC OBJECTS. 61

cover, and carefully place upon it a small streak of Canada balsam
from one end to the other. This, if laid on the cell with one
edge first, and then gradually lowered until it lies flat, will drive
all the air before it, and prevent any bubbles from being included
in the cell. It can be easily put on so neatly as to require no
cleaning when dry. If the cover is pressed down too rapidly, the
balsam will flow over it, and require to be cleaned off' when hard-
ened, for it cannot be done safely while fluid at the edges."

Sometimes with every care bubbles are enclosed in the balsam
injuring objects which are perhaps rare and valuable. The whole
slide must then be immersed in turpentine until the cover is
removed by the solution of the balsam ; and the object must be
cleansed by a similar steeping. It may then be remounted as if
new in the manner before described.

The balsam and chloroform described in Chapter I. is thus used ;
and where the object is thin, the mounting is very easily accom-
plished. When the object is laid upon the slide with a piece of
glass upon it, and the balsam and chloroform placed at the edge
of the cover, the mixture will gradually flow into the space be-
twixt the glasses until the object is surrounded by it, and the un-
occupied portion filled. The chloroform will evaporate so quickly
that the outer edge will become hard in a very short time, when
it may be cleaned in the ordinary way. Sometimes the balsam is
dissolved in the chloroform without being first hardened; but
this is only to render it more fluid, and so give the operator less
chance of leaving bubbles in the finished slide, as the thicker the
medium is, the more difficult is it to get rid of these intruders.

It has been before mentioned that some have objected to chlo-
roform and balsam, believing that it became clouded after a cer-
tain time. Perhaps this may be accounted for in part by the fact
that almost all objects have a certain amount of dampness in them.
Others are kept in some preservative liquid until the time of
mounting, and these liquids generally contain certain salts
(Chapter IV.). If this dampness, as well as all traces of these
salts, however small, are not totally removed — the former by dry-
ing, the latter by repeated washings — the addition of chloroform
will render the balsam much more liable to the cloudiness than
when balsam alone was used, as before mentioned.

62 PREPARATION AND MOUNTING

This mode of employing the balsam, however, will not be always
applicable, as chloroform acts upon some substances which balsam
alone does not. Some salts are even soluble in it, the crystals
disappearing after a few days or weeks, whereas in the balsam
alone they are quite permanent. Experience is the only guide in
some cases, whilst in others a little forethought will be all that is
required.

The particular methods used for certain objects may be now
entered upon. Many of the Diatomacese and fossil Infusoria, as
they are sometimes termed, are mounted dry, and cleaned in the
way described in Chapter II. Others are almost always placed in
balsam, except where they are intended to be used with the lieber-
kuhn and dark background, by which means some of them are
rendered exquisitely beautiful. The usual way of mounting them
in balsam is as follows : — Take a drop of the water containing
them, place it upon the slide, and evaporate over the lamp, whilst
with a needle they may be dispersed over any space desired.
When they are thoroughly dry, drop a little balsam on one side,
and exclude the bubbles. The slide may then be warmed to such
a degree that the balsam, by lifting the glass at one end, will be
carried over the specimens, which may then be covered with thin
glass, made warm as before described. Where the objects are
quite dry, and loose upon the glass, it requires great care in plac-
ing the cover upon them, otherwise they are forced to one edge,
or altogether from under it, in the wave of the balsam. For this
reason, Professor Williamson adds a few drops of gum-water to
the last washing, which causes them to adhere sufficiently to the
glass to prevent any such mishap.

Mr. T. G. Rylands' method differs in some degree from the
above, and is, to use his own words, as follows : — Thick balsam is
preferable, and the burnt covers (see Chapter II.) to be mounted
are laid in a convenient position with the diatoms upwards. The
slides required having been carefully cleaned and marked on the
under side with a ring of ink, by the aid of a turntable about half
an inch in diameter to point out the centre, a drop of benzole is
applied by a large pin to the diatoms on the cover, so as to exclude
the air from the valves and frustules. The slide is then held over
the lamp, and when warm, a sufficiently large drop of balsam is

OF MICROSCOPIC OBJECTS. 63

put upon it, and heated until it begins to steam. If small bubbles
appear, a puff of breath removes them. The slide being held slight-
ly inclined from the operator, and the drop of balsam becoming
convex at its lower edge, the cover is brought in contact with it
at that point, gradually laid down, pressed with the forceps, and
brought to its central position. When cool the superfluous balsam
(if any) is removed with a heated knife-blade, the slide cleaned
with a little turpentine, and finished by washing in a hand-basin
with soap and water. In this process there is no delay if the bal-
sam be sufficiently thick, as the slide may be cleaned off almost
before it is cold.

It is now well known that from common chalk it is an easy
matter to obtain interesting specimens of Foraminifera. Scrape a
small quantity of chalk from the mass and shake it in water ;
leave this a few minutes, pour the water away and add a fresh
quantity, shake up as before, and repeat two or three times. Take
a little of the residue, and spread it upon the slide, and when quite
dry add a little turpentine. When viewed with a power of two
hundred and fifty diameters this will generally show the organisms
very well. If it is desired to preserve the slides, they may be then
mounted in Canada balsam. Mr. Guyon, in " Recreative Science, "
observes that the accumulation of the powder, by the action of the
rain or exposure to the atmospheric action, at the foot or any pro
jection of the chalk cliffs, will afford us better specimens than that
which is " scraped," as the organisms are less broken in the former.

When the Foraminifera arc of a larger size, though transparent
enough to be mounted in balsam, the air must be first expelled
from the interior, otherwise the objects will be altogether unsatis-
factory. To accomplish this they must be immersed in turpentii e
and submitted to the action of the air-pump. So difficult is it to
get rid of this enemy that it is often necessary to employ three or
four exhaustions, leaving them for some time under each. Wlien
all air has given place to the turpentine, they must be mounted in
the ordinary way.

Of all objects which are commonly met with, few are such gene-
ral favourites as the POLYCYSTIN^E, and deservedly so. Their
forms are most beautiful, and often peculiar — stars varying in de-
sign, others closely resembling crowns ; the Astromma Aristotelis

64 PREPARATION AND MOUNTING

like a cross, and many whose shapes no words could describe.
The greater part, perhaps, of those which are usually sold, is from
the rocky parts of Bermuda ; but they are also found in Sicily,
some parts of Africa and America. They are usually mounted in
balsam, but are equally beautiful mounted " dry" and used with
the lieberkuhn. They require as much care in cleaning as the
Diatomacese, but the process is a different one. Sometimes this
is effected by simply washing until they are freed from all extra-
neous matter, but this is seldom as effectual as it should be. In
the Microscopic Journal Mr. Furlong gives the following method
of treatment as the best he knew : —

Procure —

A large glass vessel with 3 or 4 quarts of water.

New tin saucepan holding 1 pint.

2 thin precipitating glasses holding 10 oz. each.

Take 3 oz. of dry " Barbadoes earth" (lumps are best), and break
into rather small fragments. Put 3 or 4 oz. of common washing-
soda into the tin and half fill it with water. Boil strongly, and
having thrown in the earth, boil it for half an hour. Pour nine-
tenths of this into the large glass vessel, and gently crush the re-
maining lumps with a soft bristle brush. Add soda and water as
before, and boil again ; then pour off the liquid into the large ves-
sel, and repeat until nothing of value remains. Stir the large ves-
sel with an ivory spatula, let it stand for three minutes, and pour
gently off nine-tenths of the contents, when the shells will be left,
partially freed only, like sand.

2ND PROCESS. — Put common washing soda and water into the
tin as before, and having placed the shells therein, boil for an hour.
Transfer to the large vessel as before, and after allowing it to stand
for one minute pour off. Each washing brings off a kind of" flock,"
which seems to be skins.

3RD PROCESS. — Put the shells in precipitating glass and drain
off the water until not more than J oz. remains. Add half a tea-
spoonful of bicarbonate of soda, dissolve, and then pour in gently
1 oz. of strong sulphuric acid. This liberates the " flock," &c.,
and leaves the shells beautifully transparent. Wash well now with
water to get rid of all salts and other soluble matter.

OF MICROSCOPIC OBJECTS. 65

Some of the large shells are destroyed by this method, but none
that are fit for microscopic use. An oblique light shows these ob-
jects best.

These are sometimes treated in the manner described in Chap-
ter II. where the diatoms are spoken of, but many forms are liable
to be injured by this severe process.

It has been before stated that some of the zoophytes may be
mounted dry, and others examined as opaque or transparent ob-
jects according to their substance. They are very interesting
when examined in the trough whilst living, but to preserve many
of them for future examination they must be mounted in some
preservative medium. Sometimes this may be one of the liquids
mentioned in Chapter IV., but if possible they should be kept in
balsam, as there is less danger of injury by accident to this kind of
slide. This method of mounting presents some difficulties, but I
think that all agree as to the trustworthiness of Dr. Golding Bird's
information on the subject, which appeared in the Microscopic
Journal. Of this, space forbids me to give more than a condensed
account, but I hope to omit nothing of moment to the reader for
whom these pages are written.

After stating that there are few who are not familiar with these
exquisite forms, and have not regretted the great loss of beauty
they sustain in dying, he informs us that from their so obstinate-
ly retaining air in the cells and tubes when dried, it is hardly
practicable to get rid of it ; and they also shrivel up very seriously
in the process of drying. The following plan, however, he has
found almost faultless in their preparation.

To preserve them with extended tentacles, they should be
plunged in cold fresh water, which kills them so quickly that
these are not often retracted. The specimens should be preserved
in spirit until there is leisure to prepare them ; if, however, they
have been dried, they should be soaked in cold water for a day or
two before being submitted to the following processes : —

1. After selecting perfect specimens of suitable size, immerse
them in water heated to about 120° and place them under the
receiver of an air-pump. Slowly exhaust the air, when bubbles
will arise and the water appear to be in a state of active ebullition.
After a few minutes re-admit the air and again exhaust, repeating

4*

66 PREPARATION AND MOUNTING

the process three or four times. This will displace the air from
most, if not all, of the class.

2. Remove the specimens and allow them to drain upon blotting-
paper for a few seconds ; then place them in an earthen vessel
fitted with a cover, and previously heated to about 200°. This
heat may be easily got by placing the vessel for a "short time in
boiling water, wiping it immediately before use with a thick cloth.
The specimens are then dropped into this, covered with the lid,
and immediately placed under the receiver of the air-pump, and
the air rapidly exhausted. By this means they are dried complete-
ly, and so quickly that the cells have no time to wrinkle.-

3. In an hour or two remove them from the air-pump and drop
them into a vessel of perfectly transparent camphene. This may
be quite cold when the horny, tubular polypidoms, as those of the
Sertularise, are used; but should be previously heated to 100°
when the calcareous, cellular Polyzoa are the objects to be pre-
served. The vessel should be covered with a watch-glass and
placed under the receiver, the air being exhausted and re-admitted
two or three times.

4. The slide which is to receive the specimen should be well
cleaned and warmed so as to allow the balsam to flow freely over
it. This must be applied in good quantity, and air-bubbles re-
moved with the needle-point. Take the polypidom from the
camphene, drain it a little, and with the forceps immerse it fully
in the balsam. The glass to be laid upon it should be warmed
and its surface covered with a thin layer of balsam, and then low-
ered gradually upon it, when no bubbles should be imprisoned.
A narrow piece of card-board at each end of the object for the
cover to rest upon, prevents any danger of crushing the specimen.

This mode of mounting polypidoms, &c., seems to give almost
the complete beauty of the fresh specimens. They are very beau-
tiful objects when viewed with common light, but much more so
when the polarizer is used (in the manner described a little far-
ther on).

To the above instructions there can be little to add ; but I may
here mention that some young students may not be possessed of
the air-pump, and on this account put aside all search for those
specimens which need little looking for at the seaside. Many of

OF MICROSCOPIC OBJECTS. 67

these, however, though they lose some beauty by the ordinary
mode of drying, will by steeping for some time in turpentine not
only be freed from the air-bubbles, but suffer so little contraction
that they are a worthy addition to the cabinet.

Another class of objects is the spicula met with in sponges, &c.
These are often glass-like in appearance and of various shapes ;
many are found resembling needles (whence their name) ; some
from the synapta are anchor-like, whilst others are star-like and
of complex and almost indescribable combinations. As some of
these are composed of silex and are consequently not injured by
the use of nitric acid, the animal substance may be got rid of by
boiling them in it. Those, however, which are calcareous must
be treated with a strong solution of potash instead ; but which-
ever way is used, of course they must afterwards be freed from
every trace of residue by careful washing.

These spicules may be often found amongst the sand which
generally accumulates at the bottom of the jars in which sponges
are kept by those who deal in them, and must be picked out with
a camel-hair pencil. The specimens obtained by this means will
seldom if ever require any cleaning process, as they are quite free
from animal matter, &c.

In the former chapter was noticed those insects or parts of
them which are usually mounted dry. When they are large and
too opaque to admit of the dry treatment, they must be preserved
in Canada balsam or fluid. The first of these may now be con-
sidered.

It may be here mentioned, that with these objects much heat
must not be employed, as it would in some instances give rise to
a cloudiness, and almost invariably injure them.

In killing the insect it is necessary not to rub or break any part
of it. This may be performed by placing it in a small box half
filled with fragments of fresh laurel leaves, by immersion in tur-
pentine or strong spirit, as also in solutions of various poisonous
salts. After which it may be preserved for some time in turpen-
tine or other preservative liquid (Chapter IV.) until required.
As an assistance to the student, I believe that I can do no better
that give him the plan pursued by my friend Mr. Hepworth,
whose specimens arc in every way satisfactory ; but when his me-

68 PREPARATION AND MOUNTING

tliod is used, the insects must not have been placed in turpentine
for preservation : —

" After destroying the insects in chloroform or sulphuric ether
(methylated being cheaper), wash them thoroughly in a wide-neck-
ed bottle, half-filled, with two or three waters ; the delicate ones
requiring great care. Then immerse them in liquid potash (or
Brandish's solution, which is stronger than the usual preparation),
and let them remain a longer or shorter time according to their
texture. When ready to remove, put one by one into a small
saucer of clear water, and with a camel-hair pencil in each hand
press them flat to the bottom, holding the head and thorax with
the left-hand brush, and apply pressure with the other from above
downwards, giving the brush a rolling motion, which generally
expels the contents of the abdomen from the thorax. A minute
roller of pith or cork might be used instead of the brush. In
larger objects, use the end of the finger to flatten them. Large
objects require more frequent washing, as it is desirable to remove
the potash thoroughly, or crystals are apt to form after mounting.
Having placed them on the slides with thin glass covers, tied
down with thread,* dry and immerse them in rectified spirits of
turpentine ; place the vessel under the receiver of an air-pump, and
keep it exhausted until the turpentine has taken the place of the
air-bubbles : they are then ready for the application of the balsam.
Larger objects may often with advantage be transferred to a clean
slide, as during the drying there is considerable contraction, and
an outline often remains beyond the margin showing this. When
closely corked they may remain in the spirits two or three months.
As you take them from the bottle wipe as much turpentine off as
possible before removing the thread, and when untied carefully
wipe again, placing the finger on one end of the cover whilst you
wipe the other, and vice versa. By this means you remove as
much turpentine from under the cover as is necessary ; then drop
the balsam, thinned with chloroform (see Chapter I.), upon the
slide, letting the fluid touch the cover, when it will be taken in
between the surfaces by capillary attraction ; and after pressing

* This applies to the more delicate ones, which will not bear transferring
after being once spread out and dried.

OF MICROSCOPIC OBJECTS. 69

the cover down it may be left to dry, or you may hold the slide
over a spirit-lamp for a few seconds before pressing down the
cover. If heat is not applied, they are much longer in drying but
are more transparent. If made too hot the boiling disarranges
the objects, and if carried too far will leave only the resin of the
balsam, rendering it so brittle that the cover is apt to fly off by a
fall or any jar producing sufficient percussion. Never lift the cover
up if possible, during the operation, as there is danger of admitting
air. A few bubbles may appear immediately after mounting, but
generally subside after a few hours, being only the chloroform or
turpentine in a state of vapour, which becomes condensed."

This method of preparing and mounting insects I can strongly
recommend as giving first-rate results ; but where the specimens
are small they seldom ne»ed the soaking in caustic potash which
larger ones must have. It is only necessary to leave them awhile
in turpentine, especially when they have been first dried with gen-
tle pressure between two glasses, and then mount with balsam in
the ordinary way.

Amongst the insect tribes there is abundant employment, espe-
cially for the lower powers of the microscope. But if the deep-
er wonders and beauties of the animal economy are to be sought
out and studied, it is desirable that the various parts should be set
separately, in order that they may receive a more undivided at-
tention, as well as to render them capable of being dealt with un-
der the higher powers. We will, therefore, briefly consider the
treatment which the different portions require.

The eyes of the butterflies, and indeed of almost all insects,
afford materials for a study which is complete in itself. When
examined with a tolerably high power, instead of finding each eye
with an unbroken spherical surface, it is seen that many are com-
posed of thousands of hexagonal divisions, each being the outer
surface of a separate portion termed the ocellus. In others these
divisions are square ; but in all there is a layer of dark pigment
surrounding their lower parts. The ocelli may be partly removed
from the eye, which will show how their tapering forms are ar-
ranged. But here we have to consider how to place them in bal-
sam for preservation. The eve being removed from the insect,
and the dark pigment removed by the use of a cainel-hair pencil,

70 PREPARATION AND MOUNTING

must be allowed to remain in turpentine at least for some cfayp.
The turpentine should then be renewed and the eye well washed
in it just before it is to be mounted. It may then be set in bal-
sam in the same way as any other object; — but here a difficulty
is met with. The eye being spherical upon the surface required,
must necessarily be " folded " or broken in attempting to flatten it.
This difficulty may be often overcome by cutting a number of
slits round the edges; but some object to this mode of treatment,
and where it is practicable it is much more satisfactory to mount
one in the natural rounded form and another flat. Instead, how-
ever, of mounting the organ whole, four or five slides may be pro-
cured from each of the larger ones, as those of the Dragon-fly,
&c.

The antennae also are often mounted on separate slides, as being
better suited for higher powers and more minute examination than
when connected with the insect. These two projecting organs,
issuing from the head, are jointed, and moveable at will. They
differ very much in form amongst the various species, and are well
worth the attention of the microscopist. They are usually mount-
ed with the head attached, and perhaps they are more interest-
ing when thus seen. Some few are very opaque, to prepare which
the following method has been advised : —

Bleach the antennae by soaking in the following solution for a
day or two : —

Hydrochloric acid, 10 drops.
Chlorate of potash, J drachm.
Water, 1 oz.

This will render them transparent. Wash well, dry, and mount
in Canada balsam. Instead of the above, a weak solution of
chloride of lime may be used, by which means the nerves will be
well shown. Many, however, are rendered transparent enough by
simply soaking in turpentine for a longer or shorter time. Where
the antennae, however, are "plumose," or feather-like, extreme
care is required in mounting, though the difficulty is not so great
as some seem to think. If they are first dried with gentle pres-
sure, and then subjected to the action of the air-pump in a small

OF MICROSCOPIC OBJECTS. 1

quantity of turpentine until the air is thoroughly expelled, they
can be easily finished upon the slide, especially when balsam and
chloroform are used.

Insects supply us with another series of beautiful objects, viz.,
the feet.* These are sometimes simply dried and mounted with-
out any medium, as before mentioned ; but most of them are ren-
dered much more fit for examination by using balsam in their
preservation, as it greatly increases their transparency. The
smaller kinds may be dried with gentle pressure betwixt blotting-
paper, and then immersed for some clays in turpentine, without
requiring the treatment with liquor potassae. This immersion will
render them beautifully transparent, when they may be mounted
in balsam in the usual manner.

It is, however, sometimes found difficult to fix the feet when
expanded, in which state the interest of the object is greatly in-
creased. Mr. Ralph recommends the following mode : — " First
wash the feet, while the insect is yet alive, with spirits of wine ;
then holding it by a pair of forceps close to the edge of a clean
piece of glass, the insect will lay hold of the upper surface by its
foot, then suddenly drop another small piece of glass over it, so
as to retain the foot expanded, and cut it off with a pair of scis-
sors, tie up and soak to get rid of air." Mr. Hepworth says that
he never found any difficulty in expanding the foot on a drop of
water or well-wetted slide, and laying a thin glass cover over it,
tying with thread, drying, and immersing in turpentine.

The mouth, also, with its organs, is an interesting object in
many insects. That of the common fly is often made use of, and
is comparatively easy to prepare. By pressing the head, the
tongue (as it is commonly termed) will be forced to protrude,
when it must be secured by the same means as the foot, and may
be subjected to the soaking in turpentine, and mounted as usual.
The honey-bee is, however, very different in formation, and is well
worth another slide ; indeed, even in insects of the same class, the
differences are many and interesting.

Another worthy object of study is the respiration of insects,

* See Mr. Hepworth's interesting; articles on the fly's foot in the second
and third volumes of the Microscopic Journal

72 PREPARATION AND MOUNTING

which is effected by tracheae or hollow tubes, which generally run
through the body in one or more large trunks, branching out on
every side. These terminate at the surface in openings, which
are termed spiracles, or breathing organs. The tracheae often pre-
sent the appearance of tubes constructed by a twisted thread,
somewhat resembling the spiral fibres of some plants. These are
very beautiful objects, and are generally mounted in balsam, for
which reason they are mentioned here ; but as they evidently be-
long to the " dissecting portion," they will be fully treated of in
another place.

Amongst the parasitic insects a great variety of microscopic
subjects will be found. As these are usually small, they may be
killed by immersion in spirits of turpentine ; and if at all opaque,
may be allowed to remain in the liquid until transparent enough,
and then mounted in Canada balsam.

The acarida, or mites and ticks, are well known ; none, perhaps,
better than those which are so often found upon cheese. Flour,
sugars, figs, and other eatables, are much infested by them ;
whilst the diseases called the itch in man, and the mange in animals,
are produced by creatures belonging to this tribe. These animals
are sometimes mounted by simply steeping them in turpentine,
and proceeding as with other insects. The " Micrographic Dic-
tionary" gives the following directions as to mounting parts of
these : — " The parts of the mouth and the legs, upon which the cha-
racters are usually founded, may be best made out by crushing the
animals upon a slide with a thin glass cover, and washing away
the exuding substance with water ; sometimes hot solution of
potash is requisite, with the subsequent addition of acetic acid and
further washing. When afterwards dried and immersed in Canada
balsam, the various parts become beautifully distinct, and may be
permanently preserved."

Feathers of different kinds of birds are usually mounted in bal-
sam when required to show much of the structure. This is par-
ticularly interesting when the feathers are small, as they then
show the inner substance, or pith, as it may be termed, with the
cells, &c. The " pinnae," or soft branches of the feathers, will be
found of various constructions ; some possessing hooks along one
side, whereby they fasten themselves to their neighbours ; others

OF MICROSCOPIC OBJECTS.

branching out, with straight points somewhat resembling the hairs
from certain caterpillars. But, of course, when the metallic-look-
ing gorgeous colours are all that is required to be shown, and re-
flected light used (as with the feathers of the humming-bird,
peacock, &c.), it is much better that they should be mounted dry,
as in Chapter II.

The seeds and pollen of plants are most frequently mounted dry
as mentioned in Chapter II. ; but the more transparent of the for-
mer, and the darker kinds of the latter, are perhaps better seen
in Canada balsam. There is nothing particular to be observed in
the manipulation, except that the glass cover must be applied
lightly, otherwise the grains may be crushed. There are some
objects which cannot be shown in a perfect manner when mount-
ed dry, but when immersed in balsam become so very transpa-
rent that they are almost useless. To avoid this, it has been re-
commended to stain the objects any colour that may be conve-
nient, and afterwards mount in balsam in the ordinary man-
ner.

Most objects intended for the polariscope may be mounted in
Canada balsam ; but there are some exceptions to this. Many of
the salts are soluble in this medium, or their forms so injured by
it, that glycerine or oil has to be used (see Chapter IV.) ; others
must be left in the dry form, as before mentioned ; and some few
it is impossible to preserve unchanged for any length of time.
Crystals, however, are amongst the most beautiful and interesting
subjects for polarisation ; and it is very probable that, by the aid
of the polariscope, new and valuable facts are yet to be made
known. For one who finds pleasure in form and colour, there is
a field here which will only open wider upon him as he advances ;
and instead of being in anywise a merely mechanical occupation,
it requires deep and careful study. The little here said on the
subject will show this in some degree.

With almost every salt the method of crystallization must be
modified to obtain the best forms ; I may even go further than
this, and say that it is possible to change these forms to such a
degree that the eye can perceive no relationship to exist betwixt
them. If a solution of sulphate of iron is made, a small quantity
spread evenly upon a slide, and then suffered to dry whilst in a

PREPARATION AND MOUNTING

flat position, the crystals often resemble the fronds of- the common
fern in shape. But if, whilst the liquid is evaporating, it is kept
in motion by stirring with a thin glass rod, the crystals form sepa-
rately, each rhombic prism having its angles well defined, and
giving beautiful, colours with the polarized light. Again, pyro-
gallic acid, when allowed to flow evenly over the slide in a satu-
rated solution, covers the surface in long " needles," which are
richly coloured by polarized light ; but if any small portion of
dust or other matter should form a nucleus around which these
"needles" may gatker, the beauty is wonderfully increased. A
form very closely resembling the "eye" of the peacock's tail, both
in form and colour, is then produced, which to one uninitiated in
crystallography bears very little resemblance to the original crys-
tal. From these simple facts it will be clearly seen that in this,
as in every other department, study and experience are needful to
give the best results.

To obtain anything like uniformity in the formation of crystals
upon the glass slide, every trace of grease must be removed by
cleaning with liquor potassse or ammonia immediately before using,
care als3 being taken that none of the agent is left upon the slide,
otherwise it may interrupt and change their relative position, and
even their form.

Amongst those which are generally esteemed, the most beautiful
are the crystals of oxalurate of am nD.iia. The preparation of this
salt from uric acid and ammonia is a rather difficult process, and
will not on that account be described here ; but when possessed,
a small quantity of a strong solution in water must be made, and
a little placed on the slide, and evaporated slowly. Part of the
salt will then be deposited in circles with the needle-like crystals
extending from common centres. Thay should then be mounted
in pure Canada balsam ; and, wli3n th-3 best colours are wanted,
used with the selenite plate. Of this class of crystal, salicine is
a universal favourite, and can be easily procured of most chemists.
The crystals may be produced in two ways : — A small portion of
the salt must be placed upon the slide, and a strong heat applied
underneath until fusion ensues; the matter should then be evenly
and thinly spread over the surface. In a short time the crystals
will form, and are generally larger than those procured by the

OF MICROSCOPIC OBJECTS. 75

«t

following process ; but the uncertainty is increased a little when
fusion is used, which, however, is desirable with many salts.
Secondly, mate a saturated solution of salicine, which in cold water
is effected by adding one part of the salt to eighteen parts of water.
Lay a little upon the slide, and allow it to evaporate spontaneously,
or with the aid of gentle heat. The crystals are generally uniform,
and with ordinary powers quite large enough to afford a beautiful
object. The circular shape and gorgeous colours of this crystal
have made it so great a favourite that there are few cabinets with-
out it. •

Many new forms may be procured by uniting two totally dif-
ferent salts in solution in certain proportions. This is a field af-
fording new facts and beauties; but requires some chemical know-
ledge and much perseverance to obtain very valuable results. One
of the most beautiful I have met with has been composed of sul-
phate of copper and sulphate of magnesia. The flower-like forms
and uniformity of crystallization when successful make it well
worth a few failures at first ; and as I became acquainted with
some new facts in my frequent trials, I will give the preparation
of the double salt from the beginning.

Make a saturated solution of the two sulphates, combined in the
proportion of three parts copper to one part magnesia, and then
add to the solution one-tenth of pure water. Dust or other im-
purities should be guarded against, and the slide made free from
all trace of grease by cleaning immediately beforexuse with liquor
potassse or ammonia. A drop of the solution should then be placed
upon the slide, and by a thin glass rod spread evenly upon the
surface. Heat this whilst in a horizontal position until the salt
remains as a viscous transparent substance, which will not be ef-
fected until it is raised to a high degree. The slide may now be
allowed to cool, and when this is accomplished, the flower-like
crystals will be perceived forming here and there upon the plate.
When these are at any stage in which it is wished to preserve
them, a few seconds' exposure to the fire, as warm as the hand
can comfortably bear, will stop the expansion, when the portion
which we wish to mount should be cut off from the mass of salt
by simply scratching the film around, and pure Canada balsam
with the thin glass used. Breathing upon the film, or allowing

76 PREPARATION AND MOUNTING

the slide to become cold and attract the moisture from the atmo-
sphere, will cause the crystallization to extend, and sometimes
greatly rob the effect ; so it is necessary to mount quickly when
the desired forms are obtained. As the crystals are very uncer-
tain as to the place of their formation, I may here mention that
they may be got in any part of the slide by piercing the film with
a needle-point ; but in some degree this necessarily interferes with
the centre. As the cause of this has no need to be entered into
here, and has been elsewhere discussed, I shall only give the above
directions, and say that there is a great field in this branch of study
which the microscope alone has opened.

It would be useless to enter into particulars respecting the
various salts and treatment they require, as a great difference is
effected even by the strength of the solution. There are some crys-
tals, also, which are called forth in insulated portions, showing no
formation upon the ground ; but even when mounted in any pre-
serving fluid, and unchanged for a year, a new action seems to arise,
and a groundwork is produced which bears little resemblance to
the original crystal. Sometimes this new formation adds to the
beauty of the slide ; in other cases the reverse is the result, the
slide being rendered almost worthless. This action, I believe,
frequently arises from some liquid being contained in the balsam
or other mounting medium used ; and this is rendered the more
probable by the crystallization being called forth in an hour after
the balsam diluted with chloroform is employed, whereas no
change would have taken place for months (if at all) had pure
balsam been used.

Sections of some of the salts are very interesting objects, but
the method of procuring these and their nature will be described
in Chapter V.

The scales of various fish have been before mentioned as mount-
ed " dry ;" when, however, they are required for polarising objects
they are generally mounted in balsam, and some few in liquid.
The former method will be considered here.

The eel affords a beautiful object for this purpose. The scales
are covered by a thin " skin" which may be slightly raised with
a knife and then torn off', in the same manner as the covering of
the geranium and other petals, described in Chapter II. The re-

OF MICROSCOPIC OBJECTS.

quired portion may then be removed ; or if a piece of skin can be
procured as stripped off in cooking, the scales may be easily taken
from the inner surface. They must then be washed and thorough-
ly cleaned. After drying, soak for a day in turpentine, and mount
in the ordinary manner with balsam. This is a good polarising
object ; but the interest, and I think the beauty, is increased by
procuring a piece of eel's skin with the scales in situ, washing and
drying under pressure, and mounting in balsam as before. The
arrangement of the scales produces beautiful " waves" of colour,
which are quite soothing to the eye after examining some of the
very gorgeous salts, &c.

There are many scales of fish which are good subjects for the
polariscope when mounted in balsam ; but as they require no par-
ticular treatment, they need no mention by name.

Among hairs we find some which are beautiful when mounted
in balsam and examined by polarized light. Some, when wanted
as common objects, are always used dry, as before mentioned ;
but if they are intended to be shown as polarizing objects, they
must be placed in some medium. The " Micrographic Diction-
ary" mentions a mode of making an interesting object by plait-
ing two series of white horse-hairs at an angle, mounting in bal-
sam, and using with the polariscope. All hairs, however, must be
steeped in turpentine for a short time before mounting, as they
will thus be rendered cleaner and more transparent. When this
is done, there is no difficulty in mounting them.

Many of the " tongues " of fresh-water and marine mollusca are
deeply interesting and most beautiful objects when examined by
polarized light. As these are usually mounted in balsam, I men-
tion them in this place ; but as they must be removed from the
animals by dissection, particulars respecting them will not be en-
tered into until we come to the part in which that operation is
described (Chapter V.).

The manner of preparing and mounting many of the Polyzoa
and Zoophytes has been before described ; but any notice of
polarizing objects would be incomplete without some allusion to
them. A small piece of the Flustra avicularis, well prepared, is
beautiful when examined in this manner. No selenite is needed,
and yet the colours are truly gorgeous. It is often met with upon

78 PREPARATION AND MOUNTING

shells and zoophytes of a large size, and will well repay the trou-
ble of searching for. Many of the Sertularidae are very beautiful
with polarized light, and, indeed, no ramble upon the seaside need
be fruitless in this direction.

The different starches are quite a study in themselves, and are
peculiarly connected with polarized light. They are found in the
cellular tissue of almost every plant in small white grains which
vary considerably in size ; that from the potato averages one-three-
hundredth of an inch in diameter, and that from arrow-root about
one-six-hundredth. To procure starch from any plant, the tex-
ture must first be broken up or ground coarsely ; the mass of
matter must be then well washed in gently-flowing water, and, as
all starch is totally insoluble in cold water, the grains are carried
off by the current and deposited where this is stayed. In procur-
ing it from the potato, as well as many other vegetables, it is but
necessary to reduce the substance to a coarse pulp by the aid of
a culinary "grater;" the pulp should then be well agitated in
water, and allowed to rest a short time, when the starch will be
found at the bottom, its lighter colour rendering it easily distin-
guishable from the pulp. It should, however, be washed through
two or three waters to render it perfectly clean.

These grains have no crystalline structure, but present a very
peculiar appearance when examined with polarized light. Each
grain shows a dark cross whose lines meet at the point where it
was attached to the plant, called the hilum. Round the grain,
also, a series of lines are seen, as though it were put together in
plates. This is more distinctly visible in some kinds than others.

As to the mounting of these starches there is little to be said.
If the grains are laid upon the slide, and as small a portion as pos-
sible of the balsam diluted with turpentine, as before mentioned,
be applied, they will cling to the glass and allow the pure balsam
to flow readily over them without being so liable to imprison air-
bubbles when the thin glass is put upon them.

The raphides, which were fully described in Chapter II., when
required for use with polarized light, must be mounted in balsam,
and many are found which give beautiful colours. They require
no peculiar treatment, but must be washed quite clean before put-
ting up.

OF MICROSCOPIC OBJECTS. 79

There is one class of objects for the polariscope which differs
in preparation from liny we have yet considered, and affords very
beautiful specimens. Some of the plants, including many of the
grasses and the Equisetaceae (i.e. horsetails), contain so large a
quantity of silica, that when the vegetable and other perishable
parts are removed, a skeleton of wonderful perfection remains.
This skeleton must be mounted in balsam, the method of perform-
ing which will now be considered.

Sometimes the cuticle of the equisetum is removed from the
plant, others dry the stem under pressure, whilst the grasses, of
course, require no preparation. The vegetable should be immersed
in strong nitric acid and boiled for a short time ; an effervescence
will go on as the alkalies are being removed, and when this has
ceased more acid should be added. At this point the modes of
treatment differ ; some remove the object from the acid and wash,
and having dried, burn it upon thin glass until all appears white,
when it must be carefully mounted in balsam. I think, however,
it is better to leave it in strong acid until all the substance, except
the required portion, is removed ; but this will take a length of
time, varying according to the mass, &c., of the plant. Of course,
when this latter method is used, the skeleton must be washed
from the acid, &c., before being mounted in balsam.

These siliceous cuticles are readily found. The straws of most
of the cereals, wheat, oat, &c. ; the husks, also, of some of these ;
many canes ; the equisetum, as before described ; and some of
the grasses. Many of these are everywhere procurable, so that
the student can never want material for a splendid object for the
polariscope.

In Chapter II. the scales (or hairs) which are often found upon
the leaves of plants were mentioned as beautiful objects when
mounted dry ; but some of these when detached from the leaf —
which is easily done by gently scraping it, when dried, with a
knife — present brilliant starlike and other forms, if mounted in
balsam and used with the polariscope. There is a little danger,
when placing the thin glass upon the balsam, of forcing out the
scales in the wave of matter which is always ejected ; this may be
overcome by applying to the slide, previously to placing the ob-
jects upon it, an extremely thin covering of the balsam diluted

80 PREPARATION AND MOUNTING

with turpentine as before mentioned, and thus giving them every
chance of adherence ; or by using the balsam with chloroform, as
before noticed. These scales are much more abundant than was
formerly supposed, and daily new specimens are discovered ; so
that the student should always be on the look-out for them in his
researches in the vegetable world.

Most classes of objects, and the treatment they require when
mounting them in balsam, have now been considered. The next
chapter will be devoted to the preservative liquids, and the best
methods of using them.

OF MICROSCOPIC OBJECTS. 81

CHAPTER IV.

PRESERVATIVE LIQUIDS, ETC., PARTICULARLY WHERE CELLS ARE

USED.

THERE are many objects which would lose all their distinctive
peculiarities if allowed to become dry, especially those belonging
to the fresh-water Algae, many animal tissues, and most of the
very delicate animal and vegetable substances in which structure
is to be shown. These must be preserved by immersion in some
fluid ; but it is evident that the fluid must be suited to the kind of
matter which it is intended to preserve. As it often requires
much study and trouble to obtain microscopic objects of this class,
it is well that their preservation should be rendered as perfect as
possible ; and for this reason the CELLS, or receptacles of the
fluids, should be so closed that all possibility of escape should be
prevented. The accomplishment of this is not so easy a matter
as it might appear to the inexperienced.

Before giving any directions as to the manipulation required in
mounting the objects, we must consider the different liquids and
cells which are requisite for their preservation. Of the former
there are a great number, of which the principal may be mentioned.

DISTILLED WATER is strongly recommended by many for
Diatomaceae and other Protophytes. It has been, however, stated
that confervoid growths often disturb the clearness of the liquid,
and on this account various additions are made to it. A lump of
camphor is often left in the bottle, so that the water i#ay dissolve
as much as possible. One grain of bay-salt and one of alum are
added to each ounce of water ; or a drop or two of creasote shaken
up with the ounce of water, which should be afterwards filtered.
These additions are often -made ; perhaps each of them good for
certain objects.

GLYCERINE. — Some affirm this to be one of the best preserva-
tive liquids, especially for vegetable objects ; but others think that

5

82 PREPARATION AND MOUNTING

it is much better when diluted with two parts of camphor-water,
prepared as above. *

GLYCERINE AND GUM. — This is also believed to be a very good
liquid for vegetable tissues, and is thus prepared : —

Pure gum-arabic . . 1 oz.

Glycerine . . . . 1 "

Water (distilled) . . 1 "

Arsenious acid . . 1-|- grains.

Dissolve the arsenious acid in the cold water, then the gum, add
the glycerine, and mix without bubbles.

DEANE'S COMPOUND. — This is usually deemed about the best
medium for preserving Algse, mosses, &c., and is thus prepared : —
Soak 1 oz. of best gelatine in 4 oz. of water until the- gelatine
becomes soft, when 5 oz. of honey heated to boiling-point are
added ; boil the mixture, and when it has cooled, but not enough
to become stiff, add ^ oz. rectified spirit with which 5 or 6 drops
of creasote have been well mixed, and filter the whole through
fine flannel. This compound when cold forms a stiff jelly, the use
of which will be described elsewhere.

GLYCERINE JELLY. — This mixture closely resembles the above,
but as the composition differs a little it may be mentioned here.
It is strongly recommended by Mr. Lawrance in the Microscopic
Journal, where he states " that the beautiful green of some mosses
mounted two years ago, is still as fresh as the day they were
gathered ;" and that this is the only medium he knows which will
preserve the natural colour of vegetable substances. He takes a
quantity of Nelson's gelatine, soaks it for two or three hours'in
cold water, pours off the superfluous water, and heats the soaked
gelatine until melted. To each fluid ounce of the gelatine, whilst
it is fluid but cool, he adds a fluid drachm of the white of an egg.

* Dr. Carpenter says: — " Glycerine has a solvent power for carbonate of
lime, and should not be employed when the object contains any calcareous
structure. In ignorance of this fact, the author ( Dr. C.) employed glycerine to
preserve a number of remarkably tine specimens of the pentacrinoid larva of
the Comatula, whose colours he was anxious to retain; and was extremely
vexed to find, when about to mount them, that their calcareous skeletons had
so entirely disappeared, that the specimens were completely ruined."

OF MICROSCOPIC OBJECTS. 83

He then boils this until the albumen coagulates and the gelatine
is quite clear, when it is to be filtered through fine flannel, and to
each ounce of the clarified solution add 6 drachms of a mixture
composed one part of glycerine to two parts of camphor-water.

GOADBY'S FLUID. — This- is much used in the preservation of
animal objects ; and seldom, if ever, acts upon the colours. It is
thus prepared — Bay-salt, 4 oz. ; alum, 2 oz. ; corrosive-sublimate,
4 grains. Dissolve these in two quarts of boiling water and filter.
For delicate preparations some recommend that this mixture be
reduced by the addition of an equal quantity of water ; but where
there is bone or shell in the object the above acts injuriously
upon it, in which case this fluid may be used : — Bay-salt 8 oz.,
corrosive sublimate 2 grains, water 1 quart.

THWAITES'S LIQUID. — This is recommended for the preservation
of Algae, &c., as having little or no action on the colour, and is
thus prepared : — Take one part of rectified spirit, add drops of
creasote enough to saturate it ; to this add sixteen parts of dis-
tilled water and a little prepared chalk, and filter. When filtered,
mix with an equal quantity of camphor-water (as before men-
tioned), and strain through fine muslin before using.

CHLORIDE OF ZINC SOLUTION. — In the " Micrographic Dic-
tionary " this is stated to be " perhaps the best preservative known
for animal tissues." Persons of great experience, however, have
given a very different opinion ; but it is certainly very useful
in many cases where a small degree of coagulating action is not
injurious. It is used of strengths varying according to the soft-
ness of the parts to be preserved ; the average being 20 grains of
the fused chloride to 1 oz. of distilled water. To keep this liquid
a lump of camphor may be left floating in the bottle. I have
heard complaints that this mixture becomes turbid with keeping,
but I think this must only be the case when some impurity has
got into the bottle.

CARBOLIC ACID. — This substance has not been known long
enough to warrant any decided opinion upon its merits. A solu-
tion of 1 part of acid to 20 of water has been recommended on
account of its antiseptic properties.

CASTOR OIL. — This is a very useful preservative for crystals and
other objects. Many salts are quite destroyed when Canada bal-

84 PREPARATION AND MOUNTING

sam is used with them ; but very few are acted upon by this oil.
To use it, it must be dropped in a sufficient quantity to cover the
crystal or object to be preserved with a thin coating of oil. It
may be necessary sometimes to spread it with a needle or other
instrument. The thin glass should then be carefully placed upon
it, so that all air may be excluded ; and should any oil be forced
out, owing to the quantity used being too great, it must be re-
moved with blotting paper. When the edge of the thin glass
cover and the surrounding parts of the slide are as clean as possi-
ble, a coating of sealing-wax varnish or liquid glue must be applied
and allowed to dry. A second or even a third coating may be
required, but not before the previous cover is quite dry. These
varnishes, however, are very brittle, and it is much safer, as a
finish, to use one of the tougher cements — gold-size, for instance —
which will render it doubly secure.

The above are the principal liquids, &c., used for preserving
objects in cells. The different cells may be here mentioned ; and
it is recommended that these should always be kept some time
before use in order that the cement may become perfectly dry ;
and care must bo taken that no cement be used on which the
preservative liquid employed has any action whatever.

CEMENT CELLS. — Where the object is not very thick, this kind
of cell is generally used. They are easily made with the turnta-
ble before described ; but when the objects to be preserved are
very minute, these cells need not be much deeper than the ordi-
nary circle of cement on the slide. When, however, a compara-
tively great depth is required, it is sometimes necessary to make
the wall of the cell as deep as possible, then allow it to dry and
make another addition. Of these cements gold-size is one of the
most trustworthy, and may be readily used for the shallow cells.
The asphaltum and india-rubber, before noticed, I have found
very durable when well baked, and exceedingly pleasant to work
with. It may be used of such a thickness as to give space for
tolerably large objects. Black japan also is much used. Many
cements, however, which are recommended by some writers, are
worse than useless, owing to the brittleness which renders their
durability uncertain, as sealing-wax varnish, liquid-glue, &c.

The student may feel himself at a loss in choosing the cement

OF MICROSCOPIC OBJECTS. 85

which will give him the safest cells, many of them becoming par-
tially or wholly dry in a year or two, as stated in another place.
I can only give him a few general directions, and he must then
use his own judgment. Of course it would be lost labour to
employ any cement upon which the preservative liquid has any
action whatever. It is also a good rule to avoid those in whose
composition there are any pafticles which do not become a
thorough and intimate portion, as these unreduced fragments will
almost certainly, sooner or later, prepare a road by which the
liquid will escape ; and, lastly, whatever cement he uses, the cells
are always better when they have been kept a short time before
use, as already stated.

GUTTA-PERCHA RINGS have been recommended by some, as
affording every facility for the manufacture of cells for liquids ;
but they cannot be recommended, as, after a certain length of
time, they become so brittle as to afford no safeguard against
ordinary accidents.

Often the cells must necessarily be of a large size, and for this
reason are made by taking four strips of glass of the thickness
and depth required, and grinding the places where these are to
meet with emery, so as to form a slightly roughened but flat edge.
The glass strip must also be ground on the side where it meets
the plate, and each piece cemented with the marine glue men-
tioned in Chapter I. in the following manner : — On that part of
the glass to which another piece is to be attached should be laid
thin strips of the glue ; both pieces must then be heated upon a
small brass table, with the aid of the spirit-lamp, until the strips
become melted ; the small piece is then to be taken up and placed
upon the spot to which it is to be attached, and so on until the
cell is completed. It will be found necessary to spread the glue
over the surface required with a needle or some other instrument,
so that an unbroken line may be presented to the wall of the cell,
and no bubbles formed. Too great a heat will " burn " the ma-
rine-glue, and render it brittle ; care must be therefore taken to
avoid this.

When shallow cells are required, those which are made by
grinding a concavity in the middle of an ordinary slide will be
found very convenient. The concavities are cut both circular and

86 PREPARATION AND MOUNTING

oblong; and the surface being flat, the cover is easily fastened
upon it. These are now cheap, and are very safe as to leakage.

Circular cells with a flat bottom used to be made by drilling a
hole through glass of the required thickness, and fixing this upon
an ordinary slide with marine-glue ; but the danger of breakage
and the labour were so great that this method is seldom used now,
and, indeed, the rings about to fre mentioned do away with all
necessity of it.

GLASS RINGS. — Where any depth is required, no method of
making a cell for liquids is so convenient as the use of glass rings,
which are now easily and cheaply procurable. They are made of
almost every size and depth, and, except in very extraordinary
cases, the necessity for building cells is completely done away
with. These rings have both edges left roughened, and conse-
quently adhere very well to the slide, this adherence being gene-
rally accomplished by the aid of marine glue, as before noticed
with the glass cells. Gold-size has been occasionally used for this
purpose ; and the adherence, even with liquid in the cell, I have
always found to be perfect. This method has the advantage of
requiring no heat, but the gold-size must be perfectly dry, and
the ring must have been fixed upon the slide some time before
use. Canada balsam has also been used for the same purpose, but
cannot be recommended, as when it is perfectly dry it becomes so
brittle as to bear no shock to which the slide may be ordinarily
exposed.

These are the cells which are mostly used in this branch of
microscopic mounting. The mode of using them, and the dif-
ferent treatment which certain objects require wrhen intended to
be preserved in the before-mentioned liquids, may now be inquired
into.

I may mention, however, that this class of objects is looked
upon by many with great mistrust, owing to the danger there is
of bubbles arising in the cells after the mounting has been com-
pleted, even for years. I know some excellent microscopists who
exclude all objects in cells and preservative liquids from their
cabinets, because they say that eventually almost all become dry
and worthless ; and this is no matter of surprise, for many of them
do really become so. Perhaps this is owing to the slides being

OF MICROSCOPIC OBJECTS. 87

sold before they could possibly be thoroughly dry. As to the air-
bubbles, I shall have something to say presently.

We will now suppose the cell employed is made by placing a
glass ring upon the slide with marine glue or gold-size, and is quite
dry. Around the edge of the cleaned thin glass which is to cover
it, I trace with a camel-hair pencil a ring of gold-size, and also
Ground the edge of the cell to which it is to adhere. Dr. Carpen-
ter objects to tfris, as rendering the later applications of the gold-
size liable to " run in." All danger of this, however, is complete-
ly done away with by leaving the slide and cover for awhile until
the cement becomes partially " fixed," but still adhesive enough
to perform its function {Chapter II.). With many slides this is
not accomplished in less than twenty-four hours, even if left two
or three days no injury whatever ensues ; but with other kinds an
hour is too long to leave the exposed cement, so that the opera-
tor must use his own discretion. The liquid required may be
drawn up by the mouth into the pointed tube mentioned in Chap-
ter I., and then transferred to the cell. In the various books of
instruction, the object is now to be placed in the cell ; this, how-
ever, I think a great mistake, as another process is absolutely
necessary before we advance so far. The cell, full of liquid, must
be placed under the receiver of an air-pump, and the air with-
drawn. Almost immediately it will be perceived that the bottom
and sides of the cell are covered with minute bubbles, which are
formed by the air that is held in suspension by the liquid. The
slide may now be removed, and the bubbles may require the aid
of a needle or other point to displace them, so obstinately do
they adhere to the surface of the glass. This process may be
then repeated, and one cause, at least, of the appearance of bub-
bles in cells of liquid will be got rid of. The object to be mounted
should also be soaked in one or two changes of the preservative
liquid employed, and, during the soaking, be placed under the
air-pump and exhausted. It may then be transferred to the cell,
which will probably cause the liquid to overflow a little. The
cover with the gold-size applied to the edge must then be care-
fully laid upon the cell, and slightly pressed down, so that all air-
bubbles may be displaced. The two portions of gold-size will
now be found to adhere wherever the liquid does not remain,

88 PREPARATION AND MOUNTING

although the whole ring may have been previously wet. The
outer edge of the thin glass and cell must now be perfectly dried,
and a coating of gold-size applied. When this is dry, the process
must be repeated until the cement has body enough to protect
the cell from all danger of leakage. When some preservative
liquids are used, a scum is frequently found upon the surface when
placed in the cell, which must be removed immediately before the*
cover is laid upon it.

I believe this method to be perfectly secure against leakage
when carefully performed ; and some of my friends have told
me that their experience (some years) has been equally satis-
factory.

In using some of the particular kinds of preservative liquids, it
will be found necessary to make slight change in the manipulation.
This will be best explained by mentioning a few objects, and the
treatment they require.

For the preservation of the Mosses, Algae, &c., Deane's com-
pound is much used, and considered one of the best media. The
specimen to be mounted should be immersed in the compound,
which must be kept fluid by the vessel containing it being placed
in hot water. In this state the whole should be submitted to the
action of the air-pump, as it is not an easy matter to get rid of
the bubbles which form in and around the objects. The cell and
slide must be warmed ; and heat will also be necessary to render
the gelatine, &c., fluid enough to flow from the stock-bottle. The
cell may then be filled with the compound, and the specimen im-
mersed in it. A thin glass cover must then be warmed, or gently
breathed upon, and gradually lowered upon the cell, taking care,
as with all liquids, that no bubbles are formed by the operation.
The cover may be fixed by the aid of gold-size, Japan, or any of
the usual varnishes, care being taken, as before, that all the com-
pound is removed from the parts to which the varnish is intended
to adhere.

The glycerine jelly of Mr. Lawrance, before mentioned, requires
almost a similar treatment. " The objects to be mounted in this
medium should be immersed for some time in a mixture of equal
parts of glycerine and dilute alcohol (six of water to one of
alcohol). The bottle of glycerine jelly must be placed in a cup

OF MICROSCOPIC OBJECTS. 89

of hot water until liquefied, when it must be used like Canada
balsam, except that it requires less heat. A ring of asphaltum
varnish round the thin glass cover completes the mounting."

The Infusoria (see Chapter III.) are sometimes preserved in
liquid ; but present many difficulties to the student. Different
kinds require different treatment, and consequently it is well,
when practicable, to mount similar objects in two or more liquids.
Some are best preserved in a strong solution of chloride of cal-
cium, others in Thwaites's liquid, whilst a few keep their colour
most perfectly when in glycerine alone. Many of them, however,
are so very transparent that they present but faint objects for
ordinary observance. The Desmidiacese require somewhat simi-
lar treatment, and may be mentioned here. The solution of
chloride of calcium has been strongly recommended ; but no pre-
servative liquid seems to be without some action upon them.
Both of the above classes of objects should be mounted in shal-
low cells, so as to allow as high a microscopic power as possible
to be used with them.

Many of the ZOOPHYTES which are obtained on our sea-coasts
are well preserved by mounting in cells, in the manner before
mentioned, with Goadby's fluid, or distilled water with one of the
additions noticed amongst the preservative liquids. For examina-
tion by polarized light, however, they are usually mounted in bal-
sam (see Chapter III.), whilst those in cells present a more natural
appearance as to position, &c., for common study.

As to the use of preservative liquids with the Diatomacese there
are various opinions. Some experienced microscopists say that
there is little or no satisfaction in mounting them in this way.
Dr. Carpenter, however, explains this difference by his instruc-
tions as to what method should be used when certain ends are
desired. He says : " If they can be obtained quite fresh, and it
be desired that they should exhibit as closely as possible the
appearance presented by the living plants, they should be put up
in distilled water within cement-cells ; but if they are not thus
mounted within a short time after they have been gathered, about
a sixth part of alcohol should be added to the water. If it be
desired to exhibit the stipitate forms in their natural parasitism
upon other aquatic plants, the entire mass may be mounted in

5*

90 PREPARATION AND MOUNTING

Deane's gelatine in a deeper cell ; and such a preparation is a very
beautiful object for the black-ground illumination. If, on the
other hand, the minute structure of the siliceous envelopes is the
feature to be brought into view, the fresh diatoms must be boiled
in nitric or hydrochloric acid " (which process is fully described
in Chapter II.). It is very convenient to have many of these ob-
jects mounted by two or more of the above methods ; and if they
are to be studied, this is indispensable. Mr. Hepworth once
showed me about one hundred slides which he had mounted in
various ways, for no other purpose than the study of the fly's
foot.

My friend, Mr. Rylands, successfully mounts the diatoms in the
state in which he finds them, and gave me the following method
as that which he always employs. He says that he has had no
failures, and hitherto has found his specimens unchanged. Take
a shallow ring cell of asphalt or black varnish (which must be at
least three weeks old), and on the cell, whilst revolving, add a
ring of benzole and gold-size mixed in equal proportions. In a
minute or two pure distilled water is put in the cell until the sur-
face is slightly convex. The object having been already floated
on to the cover (the vessel used for this purpose being an ordinary
indian-ink palette), is now inverted and laid carefully upon the
water in the cell. By these means the object may be laid down
without being removed. The superfluous moisture must not be
ejected by pressure, but a wetted camel-hair pencil, the size made
in an ordinary quill, being partially dried by drawing through the
lips, must be used repeatedly to absorb it, which the pencil will
draw by capillary attraction as it is very slowly turned round.
When the cover comes in contact with the benzole and gold-size
ring, there is no longer any fear of the object being removed, and
a slight pressure with the end of the cedar stick of the pencil will
render the adhesion complete, and cement the cover closely and
firmly to the cell. When dry, an outer ring of asphalt makes the
mounting neat and complete.

The Fungi have been before mentioned ; but it may be here
stated that some few of the minute forms are best preserved in a
very shallow cell of liquid. For this purpose creasote-water may
be advantageously used.

OF MICROSCOPIC OBJECTS. 91

The antennae of insects have been before noticed as being very
beautiful when mounted in balsam. This is readily accomplished
when they are large ; but those of the most minute insects are
much more difficult to deal with, and are less liable to injury when
put up in fluid. Goadby^s Fluid serves this purpose very well";
but, of course, the object must be thoroughly steeped in the liquid
before it is mounted, for a longer or shorter time according to the
thickness.

The eggs of insects afford some worthy objects for the microscope,
amongst which may be mentioned those of the common cabbage
butterflies (small and great), the meadow-brown, the puss-moth,
the tortoiseshell butterfly, the bug, the cow-dung fly, &c. These,
however, shrivel up on becoming dry, and must, therefore, be pre-
served in some of the fluids before mentioned. To accomplish
this no particular directions are required ; but the soaking in the
liquid about to be employed, &c., must be attended to as with
other objects.

Glycerine may be advantageously used for the preservation of.
various insects. These should first be cleaned with alcohol to get
rid of all extraneous matter, and then, after soaking in glycerine,
be mounted with it like other objects. This liquid may also be
used for the Entomostraca, which offer a wide field for study.
They are to be found abundantly in ponds of stagnant water, &c.
Some insects, such as May-flies, &c., are, however, often preserved
by immersion in a solution of one part of chloride of calcium in
three or four parts of water ; but this has not been recommended
amongst the " preservative liquids," as the colour, which is often
an attractive quality of this class of objects, is thereby destroyed.

We have now noticed the treatment which must be applied to
those objects which are to be preserved in liquids and cells. We
may here state that all slides of this kind should be examined at
short intervals, as they will be found now and then to require
another coating of varnish round the edge of the thin glass cover
to prevent all danger of leakage. The use of the air-pump, in the
first instance (as before recommended), and this precaution as to
the varnish, will render the 4ides less liable to leakage and air-
bubbles, which so very frequently render them almost worthless.

92 PREPARATION AND MOUNTING

CHAPTER Y.

SECTIONS AND HOW TO CUT THEM, WITH SOME REMARKS ON DIS-
SECTION.

MANY objects are almost worthless to the microscopist until tlie
extraneous matter is removed from them ; and this is frequently
difficult in the extreme to perform satisfactorily. As an instance,
certain Foraminifera may be mentioned in which the cells are
placed one upon another, consequently the object must be
reduced to a certain degree of thinness before a single uniform
layer of thes« cells can be obtained to show something of the inter-
nal arrangements.

Most animal and vegetable forms require an examination of the
separate parts before much can be known about them. The mass
must be divided into separate portions, each part intended to be
preserved being cleaned from the useless matter with which it is
surrounded. It will frequently be found necessary to make thin
sections, which from a very tender substance is no easy matter;
and much patience will be necessary to attain anything like pro-
ficiency. *

This making of sections was not until very recently entered into
by many except those belonging to the medical profession, but I
do not see why this should be so, as much may be accomplished
by a persevering and interested mind where there is time for enter-
ing into the subject. I will therefore make an attempt to give
some instructions on this subject also. We will first consider the
cutting of sections from hard substances, in which the ordinary
knife, chisel, &c., are of no avail. Most of these require no par-
ticular care in mounting, but are placed in balsam like the other
objects noticed in Chapter III. : where, however, any special treat-
ment is necessary it will be commented upon as we proceed.

SHELLS, &c. — It is seldom, if ever, necessary to possess apparatus

OF MICROSCOPIC OBJECTS. 93

for this process except a small thin saw made with a steel blade,
for which a piece of watch-spring serves very well ; a fine stone
such as is used for sharpening pen-knives ; and two smooth lea-
ther strops, one of which is to be used with putty-powder to polish
the section after grinding, and the other dry, to give the final sur-
face. It is, however, very convenient to have three or four files
of different degrees of fineness. The shell, if very thick, may be
divided by using the watch-spring saw ; and this section may then
with ordinary care be rubbed down with water on the stone until
one side of it is perfectly flat. When this is accomplished it must
be again rubbed with putty-powder upon the strop, and finally
upon the other strop without the powder. This surface will then
be finished and must be firmly united to the slide in the position
it is intended to occupy. To do this a small quantity of Canada
balsam may be dropped upon the middle of the slide and heated
over the lamp until on cooling it becomes hard ; but this must be
stopped before it is rendered brittle. Upon this the polished sur-
face must be laid, and sufficient heat applied to allow the object
to fall closely upon the slide, when slight pressure may be used
to force aside all bubbles, &c. On cooling, the adherence will be
complete enough to allow the same grinding and polishing upon
the upper surface which the lower received. Whilst undergoing
this, the section must be examined from time to time to ascertain
whether the necessary degree of thinness has been reached. When
this is the case the section should be washed thoroughly and dried.
It must then be covered, which is best done by using the ordinary
Canada balsam, as recommended in Chapter III.

Sections of some exquisitely beautiful objects are cut with much
less trouble than the above. The Orbitolite, for instance, may be
prepared in this manner. Take the object and by pressure with
the finger rub the side upon a flat and smooth sharpening stone
with water until the portion is reached which it is wished to show.
The strength of the object will easily allow this to be accomplished
with ordinary care. This side may then be attached to the glass
slide with heated balsam, as above described, and the object may
then be gently rubbed down to the degree of thinness required to
show it to the best advantage. After removing all disengaged
matter from the object by washing and thoroughly drying, it may

PKEPARATION AND MOUNTING

be mounted in balsam in the usual manner, when it is equally
beautiful as a transparent or opaque object. From this it will be
seen that in many instances where a smooth stone is found suffi-
cient for the work (which is often the case when the section is
mounted in balsam) the final process of polishing advised above
may be dispensed with, as in the Orbitolite, Nummulite, &c., <fec.
It is quite necessary that the stones on which the objects are rub-
bed be perfectly flat, otherwise one side must be acted upon before
the other, and it will be found impossible to attain anything like
uniformity. Where it is not practicable to cut a section and the
object is very thick, a coarse stone may be first used to reduce it
and the smoother afterwards.

The consideration of the cutting of sections from shells would
scarcely be deemed complete without some mention of what Dr.
Carpenter terms the decalcifying process. Muriatic acid is diluted
with twenty times its volume of water, and in this the shell is im-
mersed. After a period, differing according to the thickness of
the shell, the carbonate of lime will be dissolved away, and a pecu-
liar membrane left, showing the structure of the shell very per-
fectly. This may be mounted dry, in balsam, or sometimes in
liquid, according to the appearance of the object; but no rule can
be given. The discretion of the student, however, will enable him
to choose the most suitable method.

From some shells it is easy to divide thin plates, or " laminae,"
which require nothing but mounting in Canada balsam to show
the texture very well. In working, however, with those which
are " pearly," it will be found that experience and patience are
needed, as they are very brittle and peculiarly hard ; but a little
practice will overcome these difficulties.

Amongst the Echinodermata, which include the star-fishes, sea-
hedgehogs, &c., there are many whose outer surface is covered
with " spines," or thin projections. Some of these are sharp and
thorn-like, others blunt, longer or shorter, and, indeed, of endless
variety. In many of these, when a section is made, rings are
seen which have a common centre, with radiating supports, re-
sembling sections of some of the woods. These are very beauti-
ful objects, and methods of procuring them may now be con-
sidered. It is the best to cut as thin a section as can safely be

OF MICROSCOPIC OBJECTS. 95

got with the watch-spring saw first, when the smooth " sharpening
stone " may be used to polish one side, which is easily accomplished
with water only. When this is effected, it must be washed clean,
and thoroughly dried, and then may be united to the slide in the
same manner as before recommended for the Orbitolite, &c. If
it is ever necessary to displace it on account of inequalities, bub-
bles, or other remediable fault, this may be done by warming the
slide ; though too much heat must be avoided, otherwise fresh
bubbles will certainly be produced. The covering with thin glass,
balsam, &c., will present no difficulty to the student ; but he must
remember that the transparency is somewhat increased by this
last operation.

Corals are often treated in this way, in order to reveal their
structure. Except, however, the student has had much practice,
he will often find this a most difficult task, as many of them are
exceedingly brittle. He will find the method before described
equally applicable here, and should take both horizontal and verti-
cal sections.

COAL. — This substance is one of the most interesting objects to
the microscopist. It is, of course, of a vegetable origin ; and
though this is in many cases of such minute separate portions as
to have lost all appearance of vegetation, yet it is very frequently
met with in masses, bearing the form, even to the minute mark-
ings, of wood, in various directions. To see this and prepare it
for microscopic research, a suitable piece of coal must be obtained ;
but in every case the cutting and preparation of these sections
require great care and skill. Sometimes the coal is first made
smooth on one side, fastened to the glass, reduced to the requisite
degree of thinness, and finished in the method before described.
This mode of treating it is sometimes, however, very tantalizing,
as, at the last moment, when the section is about thin enough, it
often breaks up, and so renders the trouble bestowed upon it
fruitless. The dark colour and opacity of coal render an extra-
ordinary thinness necessary, and so increase the liability to this
accident.

Perhaps the best method which can be pursued is that recom-
mended in the " Micrographic Dictionary," which is as follows : —
" The coal is macerated for about a week in a solution of carbonate

96 PREPARATION AND MOUNTING

of potash ; at the end of that time it is possible to cut tolerably
thin slices with a razor. These slices are then placed in a watch-
glass with strong nitric acid, covered and gently heated; they
soon turn brownish, then yellow, when the process must be ar-
rested by dropping the whole into a saucer of cold water, else the
coal would be dissolved. The slices thus treated appear of a
darkish amber colour, very transparent, and exhibit the structure,
when existing, most clearly. We have obtained longitudinal
and transverse sections of coniferous wood from various coals in
this way. The specimens are best preserved in glycerine in cells ;
we find that spirit renders them opaque, and even Canada balsam
has the same defect. Schulz states that he has brought out the
cellulose reaction with iodine, in coal treated with nitric acid and
chlorate of potash."

Cannel-coal is so close and firm in its structure as to be much
used instead of jet in the manufacture of ornaments ; it takes a
beautiful polish, and consequently presents the student with none
but ordinary difficulties in getting sections of it. Its formation is
somewhat different from that of coal, sometimes showing the transi-
tion very clearly.

In flint there are often found remains of sponges, shell, Dia-
tomacese, &c. ; but to show these well, sections must be cut and
polished by the lathe and wheel of the lapidary, which the micro-
scopic student seldom possesses. Thin chippings may, however,
be made, which when steeped in turpentine and mounted in bal-
sam, will frequently show these remains very well.

Teeth are very interesting objects to all microscopists, more
especially to those who give much study to them ; as the class
of animal may very frequently be known from one solitary re-
maining tooth. To examine them thoroughly, it is necessary to
cut sections of them ; but this is rather difficult to perform well,
and needs some experience. Some instructions, however, will at
least lessen. these difficulties, and we will now endeavour to give
them.

It is generally thought that Canada balsam injures the finer
markings of these sections, consequently they are almost invariably
mounted dry. A thin piece is first cut from the tooth with, the
saw of watch-spring before mentioned, if possible ; but should the

OF MICROSCOPIC OBJECTS. 97

substance be too hard for this, the wheel and lathe must be used
with diamond dust. If this cannot be procured, there is no alter-
native but to rub down the whole substance as thin as practica-
ble on some coarse stone or file. The surface will then be rough ;
but this may be much reduced by rubbing upon a flat sharpening
stone with the finger, or a small piece of gutta-percha, upon the
object to keep it in contact. The scratches may be much lessened
by this, but not so thoroughly removed as microscopic examina-
tion requires in dry sections. It must, therefore, be polished with
the putty-powder and dry strop, as recommended in the working
of the shell-sections. The other side of the section of the tooth
may then be rubbed down to the requisite thinness, and polished
in the same manner, when the dust and other impurities must be
removed by washing, after which the section must be carefully
dried and mounted. Some of these sections are equally interest-
ing as opaque or transparent objects.

The dentine of the teeth may be calcified by submersion of the
section in dilute muriatic acid; after drying and mounting in
Canada balsam it presents a new and interesting appearance,
showing the enamel fibres very beautifully when magnified about
three hundred diameters. A friend tells me that after submer-
sion of the whole tooth hi the acid he has been able to cut sections
with a razor.

SECTIONS OF BONE. — With the aid of the microscope few frag-
mentary remains have proved so useful to the geologist and stu-
dents of the fossil kingdom as these. From a single specimen
many of our naturalists can tell with certainty to what class of
animal it has once belonged. To arrive at this point of knowledge
much study is necessary, and sections of various kinds should be
cut in such a manner as will best exhibit the peculiarities of forma-
tion. The methods of accomplishing this will now be considered.
It may, however, be first mentioned that the chippings of some
bones will be found useful now and then, as 'before stated with
flint, though this is by no means a satisfactory way of proceeding.
Sometimes the bones may be procured naturally so thin that they
may be examined without any cutting ; and only require mount-
ing dry or in fluid, as may be found the best.

When commencing operations we must provide the same ap-

98 PREPARATION AND MOUNTING

paratus as is needed in cutting sections of teeth, before described.
A fine saw, like those used for cutting brass, &c. ; two or three
flat files of different degrees of coarseness ; two flat " sharpening "
stones ; and a leather strop with putty-powder for polishing. As
thin a section as possible should first be cut from the part re-
quired by the aid of the fine saw ; and it is better when in this
state to soak it for some short time in camphene, ether, or some
other spirit to free it from all grease. With the aid of a file we
may now reduce it almost to the necessary degree of thinness, and
proceed as before recommended with teeth. The " sharpening "
stone will remove all scratches and marks sufficiently to allow it
to be examined with the microscope to see if it is ground thin
'.enough ; and if it is to be mounted dry we must polish it with
putty-powder and water upon the strop to as high a degree as
possible, and having washed all remains of polishing powder, &c.,
from the section- we must place it upon the slide and finish it as
described in Chapter II.

If the bone is not sufficiently hard in its nature to bear the above
method of handling whilst grinding and polishing — as some are
far more brittle than others — as thin a section as possible must
first be cut with the saw, and one surface ground and polished.
The piece must then be dried and united to the glass by heated
balsam in the same manner as shells, &c. After which the super-
abundance of balsam must be removed from the glass ; then rub
down upon the stone and strop as before. When the polishing is
completed the whole slide must be immersed in chloroform, ether,
or some other spirit, to release and cleanse the section, when it
may be mounted as the one above mentioned.

Some have recommended a strong solution of isinglass to affix
the half-ground teeth or bones to the glass as causing them to
adhere very firmly and requiring no heat, and also being readily
detached when finished.

The reason why the sections of bone are usually mounted dry
is that the " lacunce" bone cells, and canaliculi (resembling minute
canals) show their forms, &c., very perfectly in this state, as they
are hollow and contain air, whereas if they become filled with
liquid or balsam — which does sometimes occur — they become
almost indistinguishable. There are some dark specimens, however,

rQF MICROSCOPIC OBJECTS. 99

where the cells are already filled with other matter, and it is well
to mount these with balsam and so gain a greater degree of trans-
parency.

To gain a true knowledge of the structure of bone, sections must
be cut as in wood, both transversely and longitudinally ; but with
fossil bones, without the lapidary's wheel, &c., it is a laborious
task, and indeed can seldom be properly accomplished. In this
place, also, it may be mentioned that by submitting bone to the
action of muriatic acid diluted ten or fifteen times with water, the
lime, &c., is dissolved away and the cartilage is left, which may
be cut into sections : in caustic potash the animal matter is got
rid of. Both of these preparations may be mounted in fluid.

The method of cutting thin sections of bone may be also em-
ployed with the stones of fruit, vegetable ivory, and such like sub-
stances ; many of which show a most interesting arrangement of
cells, especially when the sections are transverse. Most of these
objects present a different appearance when mounted dry to that
which they bear when in balsam, owing to the cells becoming fill-
ed ; and to arrive at a true knowledge of them we must have a
specimen mounted in both ways.

To those who study polarized light, few objects are more beau-
tiful than the sections of the different kinds of horn. We will
briefly inquire into the best method of cutting these. There are
three kinds of horn, the first of which is hard, as the stag's, and
must be cut in the same manner as bone. The second is some-
what softer, as the cow's. The third is another and still softer
formation, as the " horn" (as it is termed) of the rhinoceros. In
cutting sections of the two last we should succeed best by using
the machine invented for these purposes which I shall shortly de-
scribe when the method of cutting wood is considered. To aid
us in this when the horn is hard it must be boiled for a short time
in water, when the cutting will be more easily -accomplished. The
sections should be both transverse and longitudinal, those of the
former often showing cells with beautiful crosses, the colours with
the selenite plate being truly splendid. Of this class the rhino-
ceros horn is one of the best ; but the buffalo also affords a very
handsome object. The cow's, and indeed almost every different
kind of horn, well deserves the trouble of mounting. Whalebone,

100 PREPARATION AND MOUNTING

when cut transversely, strongly resembles those of the third and
softer formation. All these are best seen when .mounted in Canada
balsam, but care must be taken that they have been thoroughly
dried after cutting, and then steeped in turpentine.

An interesting object may also be procured from whalebone by
cutting long sections of the hairs of which it is composed. Down
the centre of each hair we shall find a line of cells divided from
one another very distinctly. And (as recommended in the " Mi-
crographic Dictionary ") if whalebone be macerated twenty-four
hours in a solution of caustic potash it will be softened, and by
afterwards digesting in water, the outer part will be resolved into
numerous transparent cells, which will show more plainly the
structure of this curious substance.

In a former chapter, hairs were mentioned, their many and in-
teresting forms, and their beauty when used with polarized light.
The sections of them, however, are no less a matter of study, as
this mode of treatment opens to sight the outer " casing," and
the inner substance somewhat resembling the pith of plants.

It would be out of place to enter into the description of the
different forms met with ; but the ways in which sections are to
be procured may be glanced at. If transverse sections are required,
some place a quantity of hairs betwixt two flat pieces of cork,
which by pressure hold them firmly enough together to allow the
required portions to be cut with a razor. • Others take a bundle
of the hairs and dip it into gum or glue, which gives it when dry
a solidity equal to wood. Sections of this are then cut with the
machine mentioned a little further on, and these may be mounted
in balsam. The human hair is easily procured in the desired sec-
tions by shaving as closely as possible a second time and cleansing
from the lather, &c., by carefully washing. Most hairs, however,
should be examined both transversely and longitudinally. It is
not difficult to procure the latter, as we may generally split them
with the aid of a sharp razor. In a great number of hairs there
is a quantity of greasy matter which must be got rid of by soak-
ing in ether or some other solvent before mounting.

We may next consider the best method of procuring sections of
wood, which must be cut of such a degree of thinness as to form
transparent objects, and so display all the secrets of their struc-

OF MICROSCOPIC OBJECTS. 101

ture. There is no monotony in this study, as the forms are so
various, and the arrangement of the cells and woody fibre so dif-
ferent, that the microscopist may find endless amusement or study
in it. From a single section the class of trees to which it has be-
longed may be known, often even when the wood is fossil. The
apparatus best adapted for cutting these sections is made as fol-
lows : — A flat piece of hard wood, about six inches long, four
wide, and one thick, is chosen, to which another of the same size
is firmly fixed, as as to form in a side view, the letter T. On
one end of the upper surface is fastened a brass plate, perfectly
flat, in the centre of which a circular opening is cut about half an
inch in diameter. Coinciding with this opening is a brass tube,
fixed in the under side of the table (if it may be termed so). This
tube is so cut at the bottom as to take a fine screw. Another
screw is also placed at the same end of the " table," which works
at right angles to this, so that any substance in the tube may be
wedged firmly by working this last screw. To use this instru-
ment, the piece of wood or other object of which a section is re-
quired must be placed in the tube, when, by turning the screw
underneath, the wood is raised above the brass plate more or less
as wished, and by using the screw at the end, it is held firmly in
the same position. With a flat chisel the portion of the object
which projects above the surface of the brass plate may now be
cut off, and by means of the bottom screw another portion may
be raised and treated in the same manner. As to the thickness
of which objects should be cut, no proper directions can be given,
as this differs so greatly that nothing but experience can be any
guide. The same thickness can be obtained by working the screw
underneath in uniform degrees, the head being marked for this
purpose ; and when the substance to be cut is very much smaller
than the hole in the brass plate, it may be wedged with cork.

As this instrument is peculiarly adapted for cutting wood
(though used for other substances, as before mentioned), I shall
notice a few particulars concerning this branch of sections. It
may here be remarked, that to obtain anything like a true know-
ledge of the nature of wood, it should be cut and examined in at
least two directions, across and along. The piece of wood is often
placed in spirits for a day or two, so that all resinous matter may

102 PREPARATION AND MOUNTING

be dissolved out of it ; it must then be soaked in water for tlie
same length of time, so as to soften and render it easy to cut.
Sections are obtained in the manner described above, but often
curl to such a degree as to make it necessary to immerse them in
water, from which they may be taken and dried under slight pres-
sure. They are often mounted dry, and require no care beyond
other objects, as in Chapter II. Some, however, are best mounted
in balsam, particularly the long sections when used for the pola-
riscope ; these must be soaked in turpentine, and the greatest
care taken that all air bubbles are got rid of. Others are thought
to be most useful when mounted in shallow cells with some of the
preservative liquids mentioned in Chapter IV. — weak spirit and
water, chloride of calcium solution of the strength of one part of
the salt to three parts of distilled water, &c.

The above "section-cutter" may not be within the reach of
every student, nor is it absolutely necessary ; though where any
great number of specimens is required it is very useful, and insures
greater uniformity in the thickness. Many employ a razor for the
purpose, which must always be kept sharp by frequent stropping.
Sections of leaves also may be procured by the same means,
though, as before mentioned, they are sometimes easily divided
by stripping the coatings off with the fingers. The cells which
come to sight by cutting some of the orchideous plants are most
interesting. To cut these leaves they may be laid upon a flat
piece of cork, thus exposing the razor to no danger of injury by
coming in contact with the support. It may be mentioned here
that the razor may also be used in cutting sections of the rush,
than which a more beautiful object can scarcely be found when
viewed transversely, as it shows the stellate arrangements of the
ducts to convey the liquids to the different parts of the plants very
clearly. This should be mounted dry. In the same way sections
of the leaf-stalks of ferns may also be cut, some of which, as Dr.
Carpenter states, show the curious ducts very beautifully, especially
when cut rather obliquely.

When sections of the softer substances are required, no instru-
ment can be compared with " Valentin's knife," which consists of
two steel blades lying parallel with one another and attached at
the lower end. The distance of separation may be regulated at

OF MICROSCOPIC OBJECTS. 103

will by a small screw near the handle. When, therefore, a sec-
tion is wanted, the substance must be cut through, and betwixt
the blades a thin strip will be found, which may be made of any
thickness, according to the distance of their separation. By
loosening the screw the blades may be extended, and the section
may be floated out in water if the damp will riot injure it. The
knife cuts much better if dipped in water immediately before use
and also when the substance to be operated upon is wet, or even
under water altogether ; but care must be taken, after use, to clean
the blades thoroughly and oil them before laying by, if the place
is at all damp. This instrument is most useful in such subjects
as anatomical preparations where the sections are required to show
the position of the different vessels, &c. ; but, as before stated,
is very valuable for all soft substances. As an instance of this, it
may be mentioned, that it is frequently used in cutting sections
of sponges ; but as these are often very full of spicula, &c., it is
much better to press the sponge flat until dry, and then cut off
thin shavings with a very sharp knife ; these shavings will expand
when placed in water. After this they may be laid betwixt two
flat surfaces and dried, when they may be mounted as other dry
objects, or, when desirable, in balsam.

Valentin's knife is very much used in taking sections of skin,
which are afterwards treated with potash solution, acids, &c., to
bring out in the best way the different portions. Dr. Lister's
mode, however, of getting these is thus given in the Microscopic
Journal: — "But I afterwards found that much better sections
could be obtained from dried specimens. A portion of shaved
scalp being placed between two thin slips of deal, a piece of
string is tied round them so as to exercise a slight degree of com-
pression ; the preparation is now laid aside for twenty-four hours,
when it is found to be dried to an almost horny condition. It
then adheres firmly by its lower surface to one of the slips, and
thus it can be held securely, while extremely thin and equable
sections are cut with great facility in any plane that may be
desired. These sections, when moistened with a drop of water
and treated with acetic acid, are as well suited for the investiga-
tion of the muscular tissue as if they had not been dried."

There are many who almost confine their attention to polarized

104 PREPARATION AND MOUNTING

light and its beautiful effects. Such would not deem these efforts
to aid the student in cutting sections complete without some
notice of those which are taken from various crystals, in order to
display that curious and beautiful phenomenon, the rings with a
cross. The arrangement of these is somewhat changed by the
crystal which affords the section ; but nitrate of potash gives two
sets of rings with a cross, the long line of which passes through
both, the short line dividing it in the middle.

The process of cutting these sections is rather difficult, but a
little care and perseverance will conquer all this. The following
is extracted from the Encyclopaedia Metropolitana : — " Nitre crys-
tallizes in long six-sided prisms whose section, perpendicular to
their sides, is the regular hexagon. They are generally very much
interrupted in their structure ; but by turning over a considera-
ble quantity of the ordinary saltpetre* of the shops specimens
are readily found which have perfectly transparent portions of
some extent. Selecting one of these, cut it with a knife into a
plate above a quarter of an inch thick, directly across the axis of
the prism, and then grind it down on a broad wet file till it is
reduced to about one quarter or a sixth of an inch thick, smooth
the surface on a wet piece of emeried glass, and polish on a piece
of silk strained very tight over a strip of plate-glass, and rubbed
with a mixture of tallow and colcothar of vitriol. This operation
requires practice. It cannot be effected unless the nitre be applied
wet and rubbed till quite dry, increasing the rapidity of the fric-
tion as the moisture evaporates. It must be performed in gloves,
as the vapour from the fingers, as well as the slightest breath,
dims the polished surface effectually. With these precautions a
perfect vitreous polish is easily obtained. We may here remark,
that hardly any two salts can be polished by the same process.
Thus, Rochelle-salt must be finished wet on the silk, and instantly
transferred to soft bibulous linen and rapidly rubbed dry. Experi-
ence alone can teach these peculiarities, and it is necessary to
resort to contrivances (sometimes very strange ones) for the pur-

* Sometimes the saltpetre of the shops is nitrate of soda, and as this is
slightly deliquescent, it is well to be certain that we have the nitrate of potash,
which is free from this defect.

OF MICROSCOPIC OBJECTS. 105

pose of obtaining good polished sections of soft crystals, especially
of those easily soluble in water.

" The nitre is thus polished on both its surfaces, which should
be brought as near as possible to parallelism."

Some sections of the naturally formed crystals also show the
" rings " very well, — as Iceland Spar, which gives a single ring
and cross ; but the difficulty of cutting and polishing them is
almost too great for the amateur, and must be left to the lapi-
dary. This curious phenomenon, however, may be seen by using
a plate of ice uninterruptedly formed of about one inch in thick-
ness.

Before concluding these remarks on sections, I must mention
a few difficulties which may be met with, and their remedies.
The foremost of these is the softness of some objects, which have
not resistance enough in themselves to bear cutting even with the
sharpest instruments. This may often be removed by soaking in
a solution of gum, and then drying, which will render the sub-
stance firm enough to be cut, when the sections must be steeped
in water, and the gum thus got rid of. Small seeds, &c., may be
placed in wax when warmed, and will be held firmly enough when
it is again cold to allow of them being cut into sections, &c.
And, lastly, where a substitute for a microscopist's hand-vice is
required, a cork which fits any tube large enough may be taken
and split, the object being then placed between the two parts,
and the cork thrust into the tube, a sufficient degree of firmness
will be obtained to resist any necessary cutting, &c.

DISSECTION. — As I stated at the commencement of this chapter,
no written instructions can enable any student to become an adept
in this branch without much experience and no little study. I
will, however, describe the necessary apparatus, and afterwards
mention the mode of treatment which certain objects require.

A different microscope is manufactured for the purpose of dis-
section, most first-rate makers having their own model. The
object-glasses of many of these are simple, and consequently not
expensive ; but one of the great requisites is a stage large enough
to hold the trough, in which the operation is often performed.
Where this is the case it would scarcely be worth the expense of
getting a dissecting microscope if the student were pursuing no

6

106 PREPARATION AND MOUNTING

particular study, but merely made use of the instrument when an
object to be operated upon turned up accidentally. The ordinary
form is much improved for this purpose, by having two wooden
rests placed at the sides of the microscope, upon which the hands
may be supported when working upon the stage. These should
be weighty enough to be free from danger of moving. These sup-
ports will also be found to be a remedy against much of the weari-
ness which inevitably arises from having to sustain the hands as
well as work with them. The erector, as I before observed, is
necessary to a young student ; but with a little practice he may
work very well without it.

We will now notice some of the instruments which are most
useful in dissection. Two or three different sizes of ordinary scis-
sors should be possessed, but the shapes must be modified in
others for many purposes, as those used by surgeons : a pair with
the cutting parts bent in a horizontal direction, and another pair
slightly curved in a perpendicular ; so that parts of the substance
operated upon may be reached, which it would be impossible to
touch with straight scissors. One point of these is sometimes
blunt, and the other acute, being thus made very useful in open-
ing tubular formations. Another form of these is made, where
the blades of the scissors are kept open by a spring, the handles
being pressed together by the fingers. Where it is desirable, one
or both of these handles may be lengthened to any degree by the
addition of small pieces of wood.

THE KNIVES which are most useful are those of the smallest
kind which surgeons employ in very delicate operations. These
are made about the length of an ordinary penknife, and are fixed
in rather long nattish handles ; some are curved inwards, like the
blade of a scythe, others backwards ; some taper to a point,
whilst others again are broad and very much rounded. Complete
boxes are now fitted up by the cutlers, of excellent quality and
surprisingly cheap.

NEEDLES. — These are very useful, and should be firmly fixed in
handles as recommended in Chapter I. It is convenient to have
them of various lengths and thicknesses. If curved by heating
and bending to any required shape they may be re-hardened by
dutting them whilst hot into cold water. Dr. Carpenter also

OF MICROSCOPIC OBJECTS. 107

makes edged instruments by rubbing down needles upon a hone.
They are more pleasant to work with when short, as the spring
they have whilst long robs them of much of their firmness.

A glass syringe is also useful in many operations, serving not
only to cleanse the objects but to add or withdraw liquids from
the dissecting-trough. This trough will now be described, as many
substances are so changed by becoming dry that it is impossible
to dissect them unless they are immersed in water during the
operation. If the object is opaque and must be worked by reflect-
ed light, a small square trough may be made to the required size
of gutta-percha, which substance will not injure the edge of the
knives, &c. ; but where transparency is necessary, a piece of thin
plate-glass must be taken, and by the aid of marine glue (as ex-
plained in Chapter IV.) the sides affixed of the required depth.
As pins, &c., cannot be used with the glass troughs and the sub-
stance must be kept extended, a thin sheet of cork loaded with
lead in order to keep it under water may be used ; but this, of
course, renders the bottom opaque. When working with many
thin substances, a plate of glass three or four inches long and two
wide will serve every purpose, and be more pleasant to use than
the trough. A drop or two of water will be as much liquid as is
needed, and this will lie very well upon the flat surface. As these
are the principal apparatus and arrangements which are requisite
in dissection, the method of proceeding in a few cases may now
be noticed.

VEGETABLES. — The dissection of vegetable matter is much less
complicated than that of animal ; maceration in water being a
great assistant, and in many cases removing all necessity for the
use of the knife. This maceration may be assisted by needles, and
portions of the matter which are not required may be removed by
them. When, for instance, the spiral vessels which are found in
rhubarb are wanted, some parts containing these are chosen and
left in a small quantity of water until the mass becomes soft, and
this is more quickly effected when the water is not changed. The
mass must be then placed upon a glass plate when practicable, or
in the trough when large, and with the aid of two needles the
matter may be removed from the spiral vessels, which are plainly
seen with a comparatively low power ; and by conveying these

108 PREPARATION AND MOUNTING

to a clean slip of glass, repeating the process, and at last washing
well, good specimens may be procured. Most of these should be
mounted in some of the preservative liquids in the manner described
in Chapter IV. Many, however, may be dried on the slide, im-
mersed in turpentine, and then mounted in balsam ; but liquid is
preferable, as it best preserves the natural appearance. Certain
kinds of vegetables require a different treatment to separate these
spiral vessels. Asparagus is composed of very hard vegetable
matter, and some have recommended the stems to be first boiled,
which will soften them to such a degree that they may easily be
separated. Dilute acids are also occasionally used to effect this ;
and in some instances to obtain the raphides caustic potash may
be employed ; but after any of these agents have been made use
of, the objects must be thoroughly cleansed with water, else the
dissecting instruments (and perhaps the cell) will be injured by
the action of the remaining portion of the softening agent.

For the dissection of animal tissues it is necessary that the
instruments be in the best order as to sharpness, &c. ; and as the
rules to be observed must necessarily be somewhat alike in many
instances, the treatment required by some of the objects most
frequently mounted will now be described. We may here remark
that cartilage can be best examined by taking sections, which will
show the arrangement of the cells very perfectly. This, however,
is plainly seen in the mouse's ear without any section being
necessary. Glycerine, the preservative liquids before mentioned,
and Canada balsam are all used to mount it ; but perhaps the
first named may be preferred in many cases.

MUSCLE. — This is what is commonly called the " flesh " of ani-
mals. If a piece be laid upon the slide under the microscope,
bundles of " fibres " will be perceived, which with needles and a
little patience may be separated into portions, some of these being
"striated," or marked with alternate spaces of dark and light.
Some of the non-striated or smooth class of muscle, such as is found
in intestines, may be prepared for the microscope by immersing
for a day or two in nitric acid diluted with three or four parts of
water, and then separating with needles and mounting as soon as
possible. Sometimes 'boiling is resorted to to facilitate the sepa-
ration, and occasions little or no alteration in the material. Speci-

OF MICROSCOPIC OBJECTS. 109

mens are often taken from ihefrog and the pig, as being amongst
the best, Goadbifs solution being generally used in mounting them.
The muscle of insects also shows the striae very perfectly.

NERVE-TISSUE. — This is seldom mounted; as Dr. Carpenter
observes, "no method of preserving the nerve-tissue has been
devised which makes it worth while to mount preparations for the
sake of displaying its minute characters," but we will mention a
few particulars to be observed in its treatment. The nerve should
be taken from the animal as soon as possible after death, and laid
upon a glass slide, with a drop or two of serum if possible. The
needles may be used to clean it, but extreme delicacy is necessary.
It will be found that the nerve is tubular and filled with a substance
which is readily ejected by very slight pressure. When the nerve
is submitted to the action of acetic acid, the outer covering, which
is very thin, is considerably contracted, whilst the inner tube is
left projecting; and thus is most distinctly shown the nature of
the arrangement. Mr. Lockhart Clarke, who has made great
researches into the structure of the spinal cord, gives a part of his
experience as follows : — He takes a perfectly fresh spinal cord and
submits it to the action of strong spirits of wine. This gives the
substance such a degree of hardness that thin sections may be
readily cut from it, which should be placed upon a glass in a
liquid consisting of three parts of spirit and one of acetic acid,
which renders them very distinct. To mount these sections, they
must now be steeped in pure spirit for two hours and afterwards
in oil of turpentine, and lastly must be mounted in Canada balsam.

TRACHEA OF INSECTS. — The nature of these was described in
Chapter III., but the method of procuring them was not explained,
as this clearly belongs to " dissection." The larger tubes are
readily separated by placing the insect in water, and fixing as
firmly as possible, when the body must be opened and the viscera
removed. The tracheae may then be cleaned by the aid of a camel-
hair pencil, and floated upon a glass, where they must first be
allowed to dry, and then be mounted in balsam. Mr. Quekett
gives the following method of removing the trachea from the
larva of an insect ; — " Make a small opening in its body, and then
place it in strong acetic acid. This will soften or decompose all
the viscera, and the tracheae may then be well washed with the

110 PREPARATION AND MOUNTING

syringe, and removed from the body with the greatest facility, by
cutting away the connections of the main tubes with the spiracles
by means of fine-pointed scissors. In order to get them upon the
slide, it must be put into the fluid, and the tracheae floated upon
it ; after which they may be laid out in their proper position, then
dried and mounted in balsam." If we wish them to bear their
natural appearance, they must be mounted in a cell with Goadby's
fluid; but the structure is sometimes well shown in specimens
mounted dry. As before mentioned, these tracheae terminate on
the outside in openings termed spiracles, which are round, oblong,
and of various shapes. Over these are generally a quantity of
minute hairs, forming a guard against the entrance of dust, &c.
The forms of these are seldom alike in two different kinds of insects,
so that there is here a wide field for the student. The dissection,
moreover, is very easy, as they may be cut from the body with a
sharp knife or scissors, and mounted in balsam or fluid. Many of
the larvae afford good specimens, as do also some of the common
Coleopterous insects.

TONGUES, OR PALATES, OF MOLLUSCS. — Of the nature of these,
Dr. Carpenter gives the following description : — " The organ which
is commonly known under this designation is one of a very
singular nature ; and we should be altogether wrong in conceiving
of it as having any likeness to that on which our ordinary ideas of
such an organ are founded. For, instead of being a projecting
body, lying in the cavity of the mouth, it is a tube that passes
backwards and downwards beneath the mouth, its higher end being
closed, whilst in front it opens obliquely upon the floor of the
mouth, being, as it were, slit up and spread out so as to form a
nearly flat surface. On the interior of the tube, as well as on the
flat expansion of it, we find numerous transverse rows of minute
teeth, which are set upon flattened plates; each principal tooth
sometimes having a basal plate of its own, whilst in other instances
one plate carries several teeth." These palates, or tongues, differ
much amongst the Gasteropods in form and size, some of them
being comparatively of an immense length. Many are amongst
the most beautiful objects when examined with polarized light.
They must, however, be procured by dissection, which is usually
performed as follows : — The animal is placed on the cork in the

OF MICROSCOPIC OBJECTS. Ill

dissecting-trough before mentioned, and the head and forepart cut
open, spread out, and firmly pinned down. With the aid of fine
scissors or knife, the tongue must be then detached from its fasten-
ings, and placed in water for a day or two, when all foreign matter
may with a little care be removed. In what way it should be
mounted will depend on the purpose for which it is intended. If
for examination as an ordinary object, it may be laid upon the
slide and allowed to dry, which arrangement will show the teeth
very well. If we wish to see it as it is naturally, it must be
mounted in a cell with Goadby's fluid ; but if it is wanted as a
polarizing object, it must be floated upon a slide, allowed to dry
thoroughly, and then Canada balsam added in the usual manner.

In the stomach, also, of some of these molluscs teeth are found,
which are very interesting objects to examine, and must be dis-
sected out in the same manner as the " tongues."

Since writing the above, Dr. Alcock (whose very beautiful
specimens prove him to be a great authority in this branch) has
published some of his experience in the second volume of the
third series of " Memoirs of the Literary and Philosophical Soci-
ety of Manchester." By his permission I make the following
extract : —

" This closes my present communication on the tongues of mol-
lusca ; but as some members may possibly feel inclined to enter
upon the inquiry themselves, I think it will not be amiss to add a
few remarks on the manner in which they are to be obtained.

" First, as to the kinds best worth the trouble of preparation.
Whelks, Limpets, and Trochuscs should be taken first. Land
and fresh-water snails can scarcely be recommended, except as a
special study, — their tongues being rather more difficult to find,
and the teeth so small that they require a high power to show
them properly. It would appear, from Spallanzani's description
of the anatomy of the head of the snail, that even he did not make
out this part, although, in his curious observations on the repro-
duction of lost parts, he must have carefully dissected more snails
than any other man.

"As to preserving the animals till wanted, they should simply
be dropped alive into glycerine or alcohol. Glycerine is perhaps
best where only the tongues are wanted ; but it leaves the ani-

112 PREPARATION AND MOUNTING

/

mals very soft ; and as it does not harden their mucus at all, they
are very slippery and difficult to work upon when so preserved.

" Then as to the apparatus required for dissection. In the first
place, all the work is to be done under water, and a common
saucer is generally the most convenient vessel to use. No kind of
fastening down or pinning out of the animal is needed ; and, in
fact, it is much better to have it quite free, that you may turn it
about any way you wish. The necessary instruments are a needle-
point, a pair of fine-pointed scissors, and small forceps ; the for-
ceps should have their points slightly turned in towards each
other.

" A word or two on the lingual apparatus generally, and on its
special characters in a few different animals, will conclude what I
have to say.

" The mode of using the tongue can be easily seen in any of
the common water-snails, when they are crawling on the glass
sides of an aquarium ; it may then be observed that from between
the fleshy lips a thick mass is protruded, with a motion forwards
and upwards, and afterwards withdrawn, these movements being
almost continually repeated. The action has the appearance of
licking ; but when the light falls suitably on the protruded struc-
ture, it is seen to be armed with a number of bright points, which
are the lingual teeth, so arranged as to give the organ the charac-
ter and action of a rasp.

"If you proceed to dissection, and open the head of one of
these mollusca (say, for instance, a common limpet), you will find
the cavity of the mouth almost filled with the thick fleshy mass,
the front of which is protruded in the act of feeding ; and on its
upper surface, extending along the middle line from back to front,
is seen the strong membranous band upon which the teeth arc
set. The mass itself consists of a cartilaginous frame, surrounded
by strong muscles ; and these structures constitute the whole of
the active part of the lingual apparatus

" But the peculiarity of the toothed membrane, which makes its
name of 'ribbon' so appropriate, is, that there is always a con-
siderable length of it behind the mouth, perfectly formed, and
ready to come forward and supply the place of that at the front,
which is continually wearing away by use.

OF MICROSCOPIC OBJECTS. 113

" In the limpet this reserve-ribbon is of great length, being
nearly twice as long as the body, and the whole of it is exposed
to view on simply removing the foot of the animal ; nothing, then,
can be easier than to extract the tongue of the common limpet.
But, unfortunately, what you find in one kind of mollusc is- not at
all what you find in another. In the Acmseas, for instance, which
are very closely related to the limpets, and have shells which can-
not be distinguished, the reserve portion of the ribbon has to be
dug out from the substance of the liver, in which it is imbedded,
that organ being, as it were, stitched completely through by a long

loop of it It might be thought a comfortable reflection

that, at all events, one end of the ribbon can always be found in
the mouth ; but in many cases this is about the worst place to
look for it. Perhaps it may appear strange that in some of the
smaller species, with a retractile trunk, a beginner may very likely
fail altogether in his attempt to find the mouth ; if, however, the
skin of the back is removed, commencing just behind the tenta-
cles, there will be very little difficulty in making out the trunk,
which either contains the whole of the ribbon, as in the whelk,
or the front part of it, as in Purpura and Murex, where a free

coil is also seen to hang from its hinder extremity In

the periwinkles the same plan of proceeding, by at once opening
the back of the animal, is best ; and on doing so, the long ribbon,
coiled up like a watch-spring, cannot fail to be found.

" In the Trochuses, and indeed in all the Scutibranchiata, one
point of the scissors should be introduced into the mouth of the
animal, and an incision made directly backwards in the middle
line above to some distance behind the tentacles; the tongue is
then immediately brought into view, lying along the floor of the
mouth."

Dr. Alcock's method of dissection will be found to differ in
some degree from the general rules before given ; and when the
tongue is dissected out he washes it for one hour (shaking it now
and then) in a weak solution of potash. After cleaning thorough-
ly in water, it must be mounted by one of the methods before
mentioned.

Amongst insects, especially the grasshopper tribe, are found
many which possess a gizzard, armed with strong teeth, somewhat

6*

114 PREPARATION AND MOUNTING

similar to those of the molluscs. It requires great nicety of mani-
pulation to obtain these for the microscope ; but it would be use-
less to attempt any description- of the process here, as the student
can only be successful by experience in dissecting objects less dif-
ficult to manage, and by using the most delicate instruments.

"We have now considered most of those objects which require
any peculiar treatment in section-cutting, &c. ; but in no branch
of microscopic manipulation is experience more necessary than in
this.

OF MICROSCOPIC OBJECTS. 115

CHAPTER VI.

INJECTION.

1. INJECTION is the filling of the arteries, veins, or other vessels
of animals with some coloured substance, in order that their natu-
ral arrangement may be made visible. This is, of course, a deli-
cate operation, and needs special apparatus, which I will now
attempt to describe.

2. Syringe. — This is usually made to contain about two ounces.
On each side of the part next to the handle is a ring, so that the
finger may be thrust through it, and the thumb may work the
piston as in an ordinary syringe. The plug of the piston must be
" packed " with wash-leather, and fit so closely as to be perfectly
air-tight ; and if, when it has been used awhile, it is found that
some of the liquid escapes past the plug into the back part of the
body, it must be repacked, which operation will be best under-
stood by examining the part These syringes are made of various
sizes, but in ordinary operations the above will be all that is
needed. The nozzle is about an inch long, and polished so accu-
rately that there is no escape when the pipes are tightly placed
upon it dry.

3. The pipes are usually about an inch long, to the end of
which are affixed thicker tubes so as to fit the nozzle, as before
mentioned, whilst a short arm projects from each side of these?
so that the silk or thread which is used to tie the artery, &c.,
upon the thin pipe may be carried round these arms, and all dan-
ger of slipping off prevented. The pipes are made of different
sizes, from that which will admit only a very fine needle (and
this will need now and then to be cleaned, or to be freed from
any chance obstruction), to that which will take a large pin.
These sizes must always be at hand, as the vessels of some sub-
jects are exceedingly minute.

116 PREPARATION AND MOUNTING

4. Stopcock. — This is a short pipe like a small straight tap,
which fits accurately upon the end of the syringe like the pipes,
and also takes the pipes in the same manner. The use of this is
absolutely necessary when the object is so large that one syringe
full of liquid will not fill it. If no preventive were used, some
part of the liquid would return whilst the syringe was being
replenished, but the stopcock is then turned as in an ordinary
tap, and all danger of this effectually removed.

5. Curved needles. — These are easily made by heating common
needles at the end where the eye is situated, and bending them
with a small pair of " pliers " into a segment of a circle half an
inch in diameter. They are, perhaps, more convenient when the
bent part is thrown slightly back where it commences. The
pointed end is then thrust into a common penholder, and the
needle needs no re-tempering, as the work for which it is wanted
is simply to convey the thread or silk under any artery or vessel
where it would be impossible to reach with the unassisted
fingers.

6. A kind of forceps, commonly known by the name of " bull-
nose forceps," will be constantly required during the process of
injecting. These are short, usually very strong, but not heavy,
and close very tightly by their own spring, which may be easily
overcome and so released by the pressure of the fingers. When
any vessel has not been tied by the operator, and he finds the
injected fluid escaping, one of these " bulldogs " may be taken up
and closed upon the opening. This will cause very little inter-
ruption, and the stoppage will be almost as effectual as if it were
tied.

7 When the ordinary mode of injection is employed, it is
necessary that the preparations be kept warm during the time
they are used, otherwise the gelatine or size which they contain
becomes stiff, and will not allow of being worked by the syringe.
For this purpose we must procure small earthenware or tin pots of
the size required, which will differ according to the kind of work
to be done ; and to each of these a loose lid should be adapted
to protect it from dust, &c. These pots must be allowed to stand
in a tin bath of water, nnder which a lamp or gas flame may be
r>laced to keep the temperature sufficiently high to insure the

OF MICROSCOPIC OBJECTS. 117

perfect fluidity of the mixture. The tin bath is, perhaps, most
convenient when made like a small shallow cistern ; but some
close it on the top to place the pots upon it, and alter the shape
to their own convenience.

8. We will now inquire into some of the materials which are
needed in this operation ; the first of which is size. This sub-
stance is often used in the form of glue, but it must be of the
very best and most transparent kind. To make the liquid which
is to receive the colours for the usual mode of injecting, take of
this glue seven ounces, and pour upon it one quart of clean
water ; allow this to stand a few hours, and then boil gently until
it is thoroughly dissolved, stirring with a wooden or glass rod
during the process. Take all impurities from the surface, and
strain through flannel or other fine medium. The weather affects
this a little as to its stiffness when cold, but this must be counter-
acted by adding a little more glue if found too liquid.

9. Instead of glue, gelatine is generally used, especially when
the work to be accomplished is of the finer kind. The propor-
tions are very different in this case, one ounce of gelatine to about
fourteen ounces of water being sufficient. This, like glue, must
be soaked a few hours in a small part of the cold water, the
remainder being boiled and added, when it must be stirred until
dissolved. A good size may be made by boiling clean strips of
parchment for awhile, and then straining the liquid whilst hot
through flannel ; but when the injections are to be transparent, it
is of the greatest importance that the size be as colourless as
possible. For this purpose good gelatine must be employed, as
Nelson's or Cox's : some persons of experience prefer the latter.

10. Colours. The size-solution above mentioned will need
some colouring matter to render it visible when injected into the
vessels of any animal, and different colours are used when two or
more kinds of vessels are so treated, in order that each " set "
may be easily distinguished by sight. The proportion in which
these colours are added to the size-solution may be given as fol-

ows : —

118 PREPARATION AND MOUNTING

11. For—

Eed 8 parts of size-solution

(by weight, to 1 part of vermilion.

Yellow. . 6 " " 1 " chrome yellow.

White . . 5 " " 1 " flake-white.

Blue . . 3 " " 1 " blue-smalt, fine.

Black ..12 " " 1 " lamp-black.

Whichever of these colours is made use of must be levigated in a
mortar with the addition of a very small quantity of water until
every lump of colour or foreign matter is reduced to the finest
state possible, otherwise in the process of injecting it will most
likely be found that some of the small channels have been closed
and the progress of the liquid stopped. When this fineness of
particles is attained, warmth sufficient to render the size quite
fluid must be used, and the colour added gradually, stirring all
the time with a rod. It may be here mentioned that where one
colour only is required, vermilion is, perhaps, the best ; and blue
is seldom used for opaque objects, as it reflects very little more
light than black.

12. When it is wished to fill the capillaries (the minute vessels
connecting the arteries with the veins), the " Micrographic Dic-
tionary " recommends the colouring matter to be made by double
decomposition. As a professed handbook would be, perhaps,
deemed incomplete without some directions as to the mode of
getting these colours, I will here make use of those given in that
work. For red, however, vermilion, as above stated, may be
used ; but it must be carefully examined by reflected light to see
whether it be free from all colourless crystals or not. It must
first be worked in a mortar, and then the whole thrown into a
quantity of water and stirred about ; after leaving it not longer
than a quarter of a minute, the larger portions will settle to the
bottom, and the liquid being poured off will contain the finer
powder. This may then be dried slowly, or added to the size
whilst wet in the manner before advised.

13. Yellow injection. — To prepare this, take —

OF MICROSCOPIC OBJECTS. 119

Acetate (sugar) of lead ; 380 grains.

Bichromate of potash 152 "

Size 8 ounces.

Dissolve the lead salt in the warm size, then add the bichromate
of potash finely powdered.

Some of the chromic acid remains free, and is wasted in this
solution, so the following is given : —

Acetate of lead 190 grains.

Chromate of potash (neutral) 100 "

Size 4 ounces.

The first of these has the deepest colour, and is the most generally
used.

14. White injection. — This is a carbonate of lead : —

Acetate of lead 190 grains.

Carbonate of potash 83 "

Size 4 ounces.

Dissolve the acetate of lead in the warm size, and filter through
flannel ; dissolve the carbonate of potash in the smallest quantity
of water, and add to the size : 143 grains of carbonate of soda
may be substituted for the carbonate of potash.

15. For blue injection, which is not, however, much used with
reflected light, as before stated, take —

Prussian blue 73 grains.

Oxalic acid 73 "

Size 4 ounces.

The oxalic acid is first finely powdered in a mortar, the Prussian
blue and a little water added, and the whole then thoroughly
mixed with the size.

16. It may here be repeated, that it is only when the capillaries
are to be filled that there is any need to be at the trouble to pre-
pare the colours by this double composition ; and, indeed, colours
ground so finely may be procured that the above instructions

120 PREPARATION AND MOUNTING

would have been omitted, had it not been supposed that some
students might find a double pleasure in performing as much of
the work as possible by their own unaided labours.

17. The process of injection may now be considered ; but it is
impossible for written instructions to supply the place of expe-
rience. I will do my best, however, to set the novice at least in
the right way. There are two kinds of injection — one where the
object and colours are opaque, and consequently fit for examina-
tion by reflected light only ; the other, where the vessels are
filled with transparent colours, and must be viewed by transmitted
light. The first of these is most frequently employed, so we will
begin with it. In the object which is to be injected a vessel of
the kind which we wish to be filled must be found ; an opening
must then be made in it to allow one of the small pipes before
mentioned to be thrust some distance within it. When this is
accomplished, thread the curved needle with a piece of silk
thread, or very fine string, which some operators rub well with
beeswax. This thread must not be too thin, else there is danger
of cutting the vessel. The cord is then carried under the inserted
pipe, and the vessel bound tightly upon it, the ends being brought
up round the transverse arms, and there tied ; so that all danger
of accidentally withdrawing the pipe is obviated. Care must now
be used in closing all the vessels which communicate with that
where the pipe is placed lest the injecting fluid escape ; and this
must be done by tieing them with silk. Should, however, any of
these be left open by accident, the bullnose forceps must be made
use of, as before recommended.

18. The part to be injected must now be immersed in warm
water, not, however, above 100° Fahrenheit, and be left until the
whole is thoroughly warmed. Whilst this is being done, the
coloured size must be made ready by the pot being placed in the
tin bath of warm water, which must be of sufficient temperature
(about 110° degrees Fahrenheit) to keep it perfectly liquid. For
the same purpose, the syringe is often tightly covered with two
or three folds, of flannel ; and, indeed, there is no part of the pro-
cess which requires more attention. If the substance to be in-
jected is too hot, it is injured ; whilst, if any of the articles are
too cold, the gelatine, or size, loses a part of its fluidity, and con-

OF MICROSCOPIC OBJECTS. 121

sequently cannot enter the minute parts. When all is prepared,
the syringe, with the stopcock attached, should be warmed, and
then filled and emptied with the injecting fluid two or three
times, care being taken that the end of the syringe be kept be-
neath any bubbles which form upon the surface. The syringe
may then be filled, and closely attached to the pipe which is tied
in the vessel. With a firm and steady pressure the piston must
be forced dowrnwards, when the substance will be perceived to
swell, and the colour show itself in places where the covering is
thin. When the syringe is almost emptied of its contents, the
stopcock must be turned to prevent any escape of the injection
from the subject. It must then be refilled, as in the first instance,
and the process repeated, I say almost emptied, because it is
well not to force the piston of the syringe quite to the bottom,
lest the small quantity of air which frequently remains be driven
into some of the vessels, and the object be injured or quite ruined.
As the injection is proceeded with, it will be found that the force
required grows greater, yet care must be taken not to use too
much, -or the vessels will burst, and render all the labour
fruitless. The movement of the piston must be occasionally
so slow as to be almost imperceptible, and for this reason
it is sometimes marked with lines about one-eighth of an inch
apart.

19. Of course, during the whole process the injecting fluid and
subject must be kept at a temperature high enough to allow the
liquid to flow freely ; and the escape of a little of it need cause
no fears to the student, as it is almost impossible to fill any sub-
ject without some loss. When the injected object has received
sufficient fluid, it should have a plump appearance, owing to all
the vessels being well filled. The vessel must then be tied up
where the pipe was inserted, and the whole left in cold water two
or three hours, after which time it may be mounted ; but it may
be well to notice a few things which the beginner ought to know
before entering into that part of the process ; and he may be
here informed that it is not necessary to mount the objects im-
mediately, otherwise it would be impossible for one person to
make use of half of any large subject, as it would be in a state
of decay long before each part could have been examined and

122 PREPARATION AND MOUNTING

separated. Large pieces should be therefore immersed in equal
parts of spirits of wine and water, or glycerine, which some think
better still, and thus preserved in bottles until time can be given
to a closer examination.

20. In operating upon large subjects, entire animals, &c., the
constant pressure required by the piston of the syringe grows
wearisome, besides occupying both hands, which is sometimes in-
convenient when working without assistance. To obviate this,
another way of driving the syringe was published in the " Micro-
graphic Dictionary " which I will quote here : — " We have there-
fore contrived a very simple piece of apparatus, which any one
can prepare for himself, and which effects the object by mechani-
cal means. It consists of a rectangular piece of board, two feet
long and ten inches wide, to one end of which is fastened an in-
clined piece of wood (equal in width to the long board, and one
foot high). The inclined portion is pierced with three holes, one
above the other, into either of which the syringe may be placed —
the uppermost being used for the larger, the lowermost for the
smaller syringe; and these holes. are of such size as freely to ad-
mit the syringe covered with flannel, but not to allow the rings
to pass through them. The lower part of the syringe is supported
upon a semiannular piece of wood, fastened to the upper end of an
upright rod, which slides in a hollow cylinder fixed at its base to a
small rectangular pieceof wood ; and by means of a horizontal wood-
en screw, the rod may be made to support the syringe at any height
required. The handle of the syringe is let into a groove in a stout
wooden rod connected by means of two catgut strings with a
smaller rod, to the middle of which is fastened a string playing
over a pulley, and at the end of which is a hook for supporting
weights, the catgut strings passing through a longitudinal slit in
the inclined piece of wood." When in use the syringe is filled
with injecting fluid, and passed through one of the three holes
which is most suitable. The object being placed so that the pipe
and syringe can be best joined, the rod and strings are set in or-
der, and a weight placed on the hook. The stopcock must then
be opened gradually, wrhen the operator will be able to judge
whether the weight is a proper one or not : if the piston is driven
with any speed, there is danger of injuring the subject, and

OF MICROSCOPIC OBJECTS. 123

less weight may be used ; if, however, the piston does not move,
more must be added.

21. Such is the method recommended by the " Micrographic
Dictionary," and perhaps it is as good as any mechanical plan
could be; but where the operator is willing to undergo the labour
of performing all this with the hand, he has a much better chance
of succeeding, because the pressure can be regulated so accurately,
and changed so quickly when requisite, that no mere machine
can compete with it, however well contrived.

22. When the beginner attempts to inject a subject, one of his
difficulties is finding the vessel from which to commence. Ano-
ther consists in distinguishing the arteries from the veins; but
this is partly removed by making a longitudinal incision in the
vessel, and with a blunt thick needle probing a little distance into
the tube. The artery will be found thicker in the coating than
the vein, and the difference is easily perceived by this mode of
testing : the vein is also of a bluer colour than the artery. I say
above, a " longitudinal incision " must be made : the reason for
this is, the artery when cut across contracts considerably, and is
lost in the adjoining substance; but where the opening is made
longitudinally all danger of this contraction is obviated.

23. The different systems of vessels are often injected with
various colours, so that their relative positions, &c., may be shown
most clearly. In some specimens, the veins are injected with
\vhite, and the arteries with red; in the kidney, the urinary tubes
are often filled with white, and the arteries with red. Then,
again, the liver affords tubes for three or four colours. But no
written instructions on the point can benefit the young student,
and he must be content for a while to employ himself with single
colours until he has gained the mechanical skill and the primary
knowledge which are necessary before he can make any advance.

24. We will now consider the best methods of mounting
injected objects. They must always be well washed in water after
they have been kept in any preservative liquid, using a camel-hair
pencil to clean the surface if necessary. Many parts when in-
jected are in masses, such as the lungs, liver, &c., of animals, and
consequently sections of these must be cut. For this purpose
Valentin's knife is very convenient, as the thickness can be regu-

124 PREPARATION AND MOUNTING

lated so easily; but where the injections are opaque, there is no
need to have the sections very thin. Some few of this kind un-
dergo comparatively little change in drying, so that the section
may be well washed and floated upon the glass slide in the place
desired, where it will dry perfectly and adhere to it. It must be
then moistened with turpentine and mounted in Canada balsam
like other objects. No great heat should be used with these pre-
parations, as it is very liable to injure them ; and some of the
colours seem to suffer a slight contraction when any great degree
of warmth is applied. There are many objects, however, which
must be seen in the mass to be understood, and, indeed, lose all
their form and beauty in drying, such as certain parts of the intes-
tines, &c. These must be mounted in fluid, with the precautions
noticed at length in Chapter IV., and for this purpose either
Goadby's fluid, the chloride of zinc solution, or spirit diluted with
ten parts of distilled water, may be employed. It is a good thing
when practicable, to mount similar objects on two separate slides,
using different preservative liquids, and taking the precaution of
marking each with the kind of liquid employed. This not only
serves as a guide to what is best for certain subjects, but if one
is injured, there will probably be a good specimen in the other.

25. It may be here mentioned that many are now mounting
sections of injected substances with the balsam and chloroform
before mentioned, instead of using balsam alone, and consider
that the labour is much lessened thereby.

26. A description of that mode of injection which is most
generally employed has now been given, but this is not the only
method of effecting our object. A most ingenious process was
invented by M. Doyers, requiring no artificial warmth, by which
many beautiful objects have been prepared. Make a solution of
bichromate of potash, 524 grains to a pint of water, and throw
this into the vessels to be injected; then take 1000 grains of ace-
tate of lead dissolved in half a pint of water, and force this into
the same vessels. A decomposition now takes place in the ves-
sels, and the yellow chromate of lead is formed. In this decom-
position, however, the acetate of potash also is formed, and as this
salt has an injurious action upon the cells, Dr. Goadby recom-
mends nitrate of lead to be used, which preserves rather than de-

OF MICROSCOPIC OBJECTS. 125

stroys them. He also advises the addition of two ounces of gela-
tine dissolved in eight ounces of water, to eight ounces of the
saturated solution of each salt ; but with this addition the hot-
water bath would be required to keep the injecting fluid liquid.

27. Many of these are best mounted in balsam, in the same
manner as those made in the ordinary way ; whilst others are
best shown when preserved in liquids, for which purpose Goadby's
fluid may be employed.

28. This mode of making injections with chromate of lead is
deemed by many the best, especially where one colour only is
employed. But it must be allowed that there is a little more
danger of failure where two separate fluids are used for the same
vessels.

29. We will now consider the best manner of making trans-
parent injections, which, for many purposes, possess an undoubted
advantage over the opaque ones. But it must be remembered
that there are certain subjects to which no transparent injection
could be applied, as they are too thick when in their natural
state, and cutting would destroy all that beauty which is shown
by the different parts in their relative adaptation. For those
objects, however, which must be cut into sections to display their
wonders, or are naturally thin — such as some of the finer tissues,
livers, kidneys, &c. — transparency is a great acquisition, and ena-
bles us to understand the arrangement of the vessels more per-
fectly. Again, another advantage is the simplicity of the process ;
no hot water is needed with some preparations, either for the
subject or the injecting fluid, which runs into the minute vessels
thoroughly and easily, whilst the cost is small.

30. For this kind of injection no colour is so commonly made
use of as Prussian blue. It is not a good one, as was before
stated, for any opaque object, as the light reflected from it appears
almost black ; yet by transmitted light no colour is more useful,
because its distinctness is equally great by artificial light and
ordinary daylight. The method of preparing this, as given by
Dr. Beale, is as follows : —

Glycerine 1 ounce.

Wood naphtha, or pyroacetic acid 1^ drachm.

Spirits of wine 1 ounce.

126 PREPARATION AND MOUNTING

Ferrocyanide (yellow prussiate) of potash. ... 12 grains.

Tincture of sesquichloride of iron 1 drachm.

Water 4 ounces.

Dissolve the ferrocyanide of potash in one ounce of the water ;
add the tincture of sesquichloride of iron to another ounce. Mix
these solutions gradually together, shaking the bottle well which
contains them — it is best to add the iron to the potash solution.
When thoroughly mixed, these solutions should produce a dark-
blue mixture, -perfectly free from any perceptible masses or flocculi.
Next mix the naphtha and spirits of wine, and add the glycerine
and the remaining two ounces of water. This must now be slowly
mixed with the blue liquid, shaking the whole well in a large
bottle whilst the two come together. The tincture of sesquichlo-
ride of iron is recommended, because it can always be obtained of
a uniform strength.

31. Dr. Turnbull used a mixture slightly different from the
above, which is made with the sulphate of iron : —

Purified sulphate of iron 10 grains.

Ferrocyanide of potassium 32 grains.

Glycerine 1 ounce.

Pyroacetic acid 1| drachm.

Alcohol 1 ounce.

Water 4 ounces.

Dissolve the sulphate of iron in one ounce of the water, gradually
add the ferrocyanide of potassium dissolved in another ounce, and
proceed as above.

32. Dr. Beale also gives us the following carmine injection to
be employed in the same way as the blue.* Take —

Carmine 5 grains.

Glycerine, with 8 or 10 drops of hydrochloric

acid ^ ounce.

* When, however, it is desirable to cut very thin sections of the injected
subject, the carmine is sometimes added to a solution of fine gelatine —
gelatine one part to water eight parts. But the warm water and mode of
proceeding which are used with the size solutions before described will bo
necessary in this case also.

OF MICROSCOPIC OBJECTS. 127

Glycerine (pure) 1 ounce.

Alcohol 2 drachms.

Water 6 drachms.

Mix the carmine with a few drops of water, and when well incor-
porated add about five drops of liquor ammonia. To this dark-
red solution about half an ounce of the glycerine is to be added,
and the whole well shaken in a bottle. Next, very gradually pour
in the acid glycerine, frequently shaking the bottle during admix-
ture. Test the mixture with blue litmus-paper, and if not of a
very decidedly acid reaction, a few more drops of acid may be
added to the remainder of the glycerine and mixed as before.
Lastly, mix the alcohol and water very gradually, shaking the
bottle thoroughly after adding each successive portion till the
whole is mixed. This fluid may be kept ready prepared, and injec-
tions made very rapidly with it.

33. The method of making injections with these colours is the
same as with the gelatine mixtures before described, except that
no heat is required, and consequently most of the trouble re-
moved. The bottle of the fluid must be well shaken immediately
before use ; and when the object is injected, we must allow it to
remain in a cool place for a few hours before cutting it. Thin
sections of the subject may be cut with Valentin's knife, as
before described, and are very beautiful transparent objects.
Some of the finer tissues, also, are shown much better by this
mode of injection than by the opaque, and are easily mounted by
washing in clean water when first separated, and floating upon a
slide, where they must be allowed to dry thoroughly. They may
then be immediately mounted in balsam, or kept in the dry state
until it is convenient to finish them ; but in many cases this keep-
ing, if too much prolonged, will injure the object. If it is desired
to transfer the section to another slide, it will be necessary to wet
it thoroughly with water. by the aid of a camel-hair pencil, and
then gently strip it off with the forceps. When it is wished to
preserve injected subjects in "masses," it must be done by im-
mersion in spirit, and the sections may be cut at leisure. Most
of these transparent objects may be mounted in Canada balsam ;
but some recommend glycerine or glycerine jelly, as allowing the

128 PREPARATION AND MOUNTING

use of a higher power in their examination, and preserving them
in a more natural form.

34. A few subjects may be noticed which are very beautiful
when injected, and amongst these are the eyes of many animals.
They must be injected by the artery in the back part, and when
the blue transparent liquid is employed, nothing can exceed the
delicate beauty which some of the membrane bears. It must,
however, be dissected with care, but well repays us for the
trouble. Water-newts and frogs are not difficult subjects, and in
their skin and other parts are many interesting objects. Amongst
the commoner animals — rats, rabbits, cats, &c. &c. — almost end-
less employment may be found, making use either of portions or
the whole animal at once. The intestines of many of these are
very beautiful. We must divide them with a pair of scissors
along the tube, and cleanse them from all the matter ; the coating
may then be laid upon a slide and any remaining impurity re-
moved with a camel-hair pencil and water. When dried it may
be mounted in balsam, and having been injected with the trans-
parent blue, its minute beauty is shown most perfectly. In in-
jecting a sheep's foot, which is a good object, the liquid should
be forced into it until a slight paring of the hoof shows the colour
in the fine channels there.

35. When the lungs of small animals are injected, the finest
fluid must be used, as some of the capillaries are so small that it
is not an easy matter to fill them properly. And before entering
upon these subjects, a certain proficiency in the mode of using the
syringe, &c., should be obtained by practising upon simpler parts.

36. No subjects are more difficult to inject than fish, owing to
the extreme softness of their tissues. Dr. Hogg recommends the
tail of the fish to be cut off, and the pipe to be put into the
divided vessel which lies just beneath the spinal column ; by which
method beautiful injections may be made. The gills, however,
are the most interesting part as microscopic objects.

37. These instructions may seem very imperfect to those who
have had much experience in this branch ; but they will remem-
ber that their own knowledge was not gained from any written
descriptions, but was forced upon them by frequent failures, some
of which probably were very disheartening. As I before stated,

OF MICROSCOPIC OBJECTS. 129

it is very difficult (if not impossible) to accomplish much without
some knowledge of anatomy.

38. I may here mention that the transparent injections sent
over from the Continent are beautifully executed by Hyrtl of
Vienna (who states that the injected fluid is composed of gelatine
and carmine), Dr. Oschatz of Berlin, the Microscopic Institute of
Wabern, Schaffer and Co. of Magdeburg, and others. Some of
these will bear examining with a high power. A friend informs
me that he measured a vessel in a rat's tongue by Hyrtl, which
was 1 -7200th of an inch in diameter, and had a clear outline with
quarter-inch objective. He has also made many experiments with
the same materials, but has as yet failed in producing perfectly
distinct outlines, there being a tendency of the colouring matter
(magenta, carmine, &c.) to diffuse itself through the coats of the
vessels into the surrounding tissues, although he has varied the
pressure from one half a pound to sixty pounds. He believes the
vessels are first washed out (injected with warm water and pres-
sure applied), then some fluid introduced which renders the arteries
impervious to the coloured fluid afterwards injected.

39. He finds that after washing out the vessels as above, the
injecting fluid is much more easily introduced. He has used a
strong solution of ?gallic acid previously to injecting with the
colouring matter (in one experiment only), and the result was
satisfactory. He puts the query, — Might not carbolic acid have a
similar effect? He has often used it with injections to preserve
the specimens, but not in sufficient quantity to act in the way indi-
cated above.

Since writing the above, Mr. J. Gr. Dale, F.C.S., and I have made
numerous experiments with carmine injection, and have at length
been favoured with what we deem success. Some of the vessels
in a kitten lately injected do not exceed l-2000th of an inch in
diameter, and present a clear outline with one-fifth objective.
There is no extravasation, neither does the colouring matter show
any grain except when a very high power is employed. The fol-
lowing is our process : —

Take 180 grains best carmine ; J fluid ounce of ammonia, com-
mercial strength, viz., 0*92, or 15° ammonia meter; 3 or 4 ounces
distilled water. Put these into a small flask, and allow them to

7

130 PREPARATION AND MOUNTING

digest without heat from twenty-four to thirty-six hours, or until
the carmine is dissolved. Then take a Winchester quart bottle,
and with a diamond mark the spot to which sixteen ounces of
water extend. The coloured solution must be filtered into the
bottle, and to this pure water should be added until the whole
is equal to sixteen ounces.

Dissolve 600 grains potash alum in ten fluid ounces of water,
and add to this, under constant boiling, a solution of carbonate of
soda until a slight permanent precipitate is produced. Filter and
add water up to sixteen ounces. Boil and add the solution to
the cold ammoniacal solution of carmine in the Winchester quart,
and shake vigorously for a few minutes. A drop of this placed
upon white filtering-paper should show no coloured ring. If much
colour is in solution the whole must be rejected, because, although
it is possible to precipitate all the colouring matter by the addi-
tion of ammonia or alum, it is not well to do so, as the physical
condition of the precipitate is thereby altered.

Supposing the precipitation to be complete, or very nearly so,
shake vigorously for at least half an hour, and allow it to stand
until quite cold. The shaking must then be renewed for some
time, and the bottle filled up with pure water.

After allowing the precipitate to settle a day, draw off the clear
supernatant fluid with a syphon. Repeat the washing until the
clear liquid gives little or no precipitate with chloride of barium.
So much water must be left with the colour at last that it shall
measure forty fluid ounces.

For the injecting fluid take twenty-four ounces of the above
coloured liquid, and three ounces of good gelatine. Allow these to
remain together twelve hours, and then dissolve by the heat of a
water bath ; after which it should be strained through fine muslin.

As this injecting fluid contains gelatine, the hot water, and
other contrivances mentioned in a former part of the chapter,
will be necessary here also, but no peculiar treatment will be
required.

OF MICROSCOPIC OBJECTS. 131

CHAPTER VII.

MISCELLANEOUS.

IT must be evident to all readers that there are various objects of
interest to the microscopist which cannot be properly placed
amongst any of the forementioned classes, but must not be omitted
in such a guide as this professes to be. Of these may be men-
tioned the circulation of the blood in various animals, the' rotary
motion of the fluid in many plants, the best means of taking
minute photographs, <fec. &c.

Perhaps the most interesting of these objects is the circulation
of the blood through the finer vessels of various parts of the ani-
mals made use of for these purposes, which parts, it is evident,
must be very transparent to afford a perfect view of this pheno-
menon. The web of the frog's foot is very frequently made use
of, but requires a certain arrangement, which we will now describe.
A piece of thin wood (Dr. Carpenter recommends cork) is taken,
about eight inches long and three wide ; about an inch from one
end is cut a hole, half or three-quarters of an inch in diameter.
The body of the frog is then placed in a wet bag, or wrapped in
wet calico, whilst the hind-foot projects ; the whole is then laid
upon the piece of wood so that the foot, which is left free, may
be extended over the hole. The web must then be spread out,
and secured either by threads to small pins on the wood, or the
pins must be driven through the web into the wood, and so kept
in position. A few bands of tape must be passed round the body,
the leg, and the wood, to prevent any disarrangement arising from
the animal starting, <fec. Care must be taken that the tape is not
too tight, else the circulation will be very slow or altogether
stopped. The wood must now be fixed upon the stage, with the
aperture under the object-glass : this is sometimes done by simply
binding it, or a spring is fixed so as to accomplish the same ob-

182 PREPARATION AND MOUNTING

ject without so much trouble. With a half-inch power the blood
may now be seen to flow very distinctly. The frog may be used
for hours if care is taken to prevent the web from becoming dry,
by wetting it with a little water from time to time. The piece
of wood or cork upon which the frog is laid is often made to give
place to the " frog-plates," supplied by opticians. These are made
of brass, somewhat resembling the piece of wood above recom-
mended, but each maker's pattern differs according to his own
taste.

The tongue of the frog is also sometimes used for the purpose
of showing the circulation of the blood, which is done in the fol-
lowing manner : — The body is wrapped with the calico, and made
fast to the plate as before, only the mouth of the frog is brought
to the opening. The tongue is then gently drawn out of the
mouth and pinned down over the aperture, when the circulation
will be well show^n. But, as Dr. Carpenter observes, the cruelty
of this mode of treatment is so repulsive that it is unjustifiable.

Tadpoles of the frog (which, of course, are only obtainable in
their season) are good subjects for showing the circulation of the
blood. They are best suited for the microscope when about one
inch long. The tadpoles of the newt and toad also are equally
suitable. They may be placed in a very shallow glass trough
with a little water, and a narrow band of linen bound lightly
round in some part not required for examination, to keep them
from moving ; or they may be laid upon a glass plate with a drop
or two of water, and a thin glass covering lightly bound upon it.
Dr. Carpenter, however, places them first in cold water, gradually
adding warm until the whole becomes about 100°, when the tad-
pole becomes rigid, whilst the circulation is still maintained. I
have not, however, found this necessary, the thin glass accom-
plishing all that is desired. The tail is generally the most trans-
parent, and shows the circulation best ; but in some of the newt
larvae the blood may be traced down to the very extremities if
they are not too old. Mr. Whitney places the tadpole upon its
back, by which means the heart and other internal arrangements
may be seen.

Amongst fishes also may be found subjects for the same pur-
pose, but they seldom furnish as good examples as those before

OF MICROSCOPIC OBJECTS. 133

mentioned, because the blood-vessels are not nearly so abundant
as in tlie foot of the frog, &c. The stickleback is, however, pro-
curable almost in any place during the summer months, and may
be laid in a shallow trough, loosely bound as the tadpole. The
tail may be covered with a piece of thin glass to prevent him
curling it to the object-glass. The power needed with this will
be about the same as with the other subjects — viz., half to quarter
inch object-glass.

It is not absolutely necessary to go to reptiles or fishes for this
curious sight, as some other animals serve Very well. In the
wings of the common bat may be found a good subject. These
must be stretched out on something resembling the frog-plate
before described, when those parts near to the bones will show
the largest vessels very clearly. The ear of a young mouse is an
illustration of the same phenomenon, but it is very difficult to fix it
in a good position, as these animals are so very timid and restless.,

Amongst insects also the same law may be observed, by placing
them in the " cage," or " live-box," so as to keep them still, but
not to injure them by too much pressure. In certain larvae this
is particularly well shown, as that of the day-fly and plumed gnat ;
but in some of these the blood is almost colourless. In the wings
also of many insects this circulation is well seen, as in those of the
common house-fly ; but as these parts become dry in a few days,
the subject should not be more than twenty-four hours old.

Somewhat approximating to the forementioned phenomenon, is
the " rotation " of fluid in the cells, or, as it is usually termed,
the circulation of the sap, of plants. This is shown in certain
vegetable growths as a constant stream of thick fluid, wherein
small globules are seen ; which stream flows round the individual
cells, or up the leaf, turning at the extremity, and down again by
a different but parallel channel. There is little or no difficulty in
showing this in many plants ; but some are, of course, better than
others, and require a different treatment; we will, therefore,
notice a few of these. Perhaps the best of all is the Vallisneria
spiralis, which is an aquatic plant, frequently grown in, but not
really belonging to, this country. As it somewhat resembles
grass, the leaf is not used in its natural state, but a thin section
cut lengthwise with a razor or other sharp instrument — this sec-

7*

134 PREPARATION AND MOUNTING

tion, however, is much better when the outer surface has been
first removed. It should then be laid upon a slide with a drop
or two of water, and covered with a piece of thin glass. Often
the cutting of the section seems to be such a shock to the leaf
that no motion is visible for awhile, but in a short time the
warmth of an ordinary sitting-room will revive it, and with a
quarter-inch object-glass the currents will be rendered beautifully
distinct. Where the " stream " is unusually obstinate the warmth
may be slightly increased, but too great heat destroys the move-
ment altogether. In the summer, any of the leaves show this
" circulation " very well ; but in the winter, the slightly yellow
ones are said to be the best.

The Vallisneria requires to be cut in sections to show this
" circulation ; " but there are many plants of which it is but
necessary to take a fragment and lay it upon a slide. The Ana-
cbaris alsinastrum is one of these : it grows in water, having
three leaves round the stem, then a bare portion, again another
three leaves, and so on. One of these leaves must be plucked
close to the stem, and laid upon a slide with a drop of water.
Thin glass should be placed upon it, and along the mid-rib of the
leaves the " circulation " may be seen most beautifully when a
good specimen has been chosen ; but it requires rather more
power than the Vallisneria. This plant is very common in many
parts of the country, a great number of our ponds and streams
being literally choked up by it. In the Cham vulgaris and two
or three of the Nitellse, &c., this phenomenon may also be seen
with no preparation except plucking a part from the stem and
laying it upon a slide as with the Anacharis. In using the Frog-
bit, the outer part of the young leaf-buds must be taken to obtain
the best specimens for this purpose ; but a section of the stem
will also show the " circulation," though not so well. The plants
before mentioned are all aquatic, but the same movement of the
globules has been observed in several kinds of land plants, as in the
hairs upon the leaf-stalks of the common groundsel ; but these do
not show it so well, nor are they so easily managed as the above.

Many microscopists who are not fortunate enough to be in the
neighbourhood of these plants (indeed the Vallisneria is a foreign
one) grow them in jars, so a few remarks as to the treatment they

OF MICROSCOPIC OBJECTS. 135

require will not be out of place. The Vallisneria requires a tem-
perature not lower than 55° or 60°, and even a higher degree
than this renders its growth quicker; and no great change must
take place : the more equable the temperature the more healthy
will the plant be. A glass jar should be taken, having an inch or
two of mould at the bottom, which must be pressed down closely,
and the plant must be set in this. Water must then be gently
poured in, so as not to disturb the mould. As this plant flou-
rishes best when the water is frequently changed, Mr. Quekett
recommends that the jar should be occasionally placed, under a
tap of water, and a very gentle stream allowed to fall into it for
several hours, by which means much of the confervoid growth
will be got rid of and the plant invigorated. The Anacharis may
be rooted in the earth like the Vallisneria, but a small detached
piece may be thrown into the jar of water and there left until
wanted. For months the " circulation " will be well shown by it,
and it will probably grow and increase. It is also very healthy in an
in-door aquarium. It is recommended that the jars in which any
of the Chara are grown should be moved about as little as possible,
as the long roots are very tender, and will not bear agitation.

An object which is interesting to the microscopist, as well as
the unscientific observer, is the growth of seeds, as it is often erro-
neously termed. A shaving of the outside of the seed is taken
and laid upon the glass slide ; a thin glass cover is then placed
upon it, and a drop of water applied to the edge of this. The
water will then gradually flow under the glass and reach the sec-
tion of the seed, when the transparent fibres will appear to spring
out and " grow " for some minutes. This, however, is produced
by the unfolding of a spiral formation in the cells, and, therefore,
has really no similarity to the true growth. The seeds of the
Salvias, Collomias, Senecio, Ruellia, &c., are well suited for the
display of this curious sight.

To watch the development of the spores of ferns, and the fer-
tilization and products, Dr. Carpenter recommends the following
mode of proceeding : — " Let a frond of a fern, whose fructification
is mature, be laid upon a piece of fine paper, with its spore-bear-
ing surface downwards ; in the course of a day or two this paper
will be found to be covered with a very fine brownish dust, which

136 PREPARATION AND MOUNTING

consists of the discharged spores. This must be carefully col-
lected, and should be spread upon the surface of a smoothed
fragment of porous sandstone ; the stone being placed in a saucer,
the bottom of which is covered with water, and a glass ' tumbler '
being inverted over it, the requisite supply of moisture is insured,
and the spores will germinate luxuriantly. Some of the prothallia
soon advance beyond the rest ; and at the time when the ad-
vanced ones have long since ceased to produce antheridia, and
bear abundance of archegonia, those which have remained behind
in their growth are beginning to be covered with antheridia. If
the crop be now kept with little moisture for several weeks and
then suddenly watered, a large number of antheridia and arche-
gonia simultaneously open, and in a few hours afterwards the
surface of the larger prothallia will be found almost covered with
moving antherozoids. Such prothallia as exhibit freshly opened
archegonia are now to be held by one lobe between the forefinger
and thumb of the left hand, so that the upper surface of the pro-
thallium lies upon the thumb ; and the thinnest possible sections
are then to be made with a narrow-bladed knife perpendicularly
to the surface of the prothallium. Of these sections, which after
much practice may be made no more than 1-1 5th of a line of
thickness, some will probably lay open the canals of the archego-
nia, and within these, when examined with a power of 200 or 300
diameters, antherozoids may be occasionally distinguished."

Another interesting object to the young microscopist is afforded
by the spores of the equiseta (or horsetails, as they are often
called). These may be obtained by shaking the higher portion of
the stems when the spores are ripe. They will then fall like
small dust, and may be placed under the microscope. The spores
are then seen to consist of a somewhat heart-shaped mass with
bands rather intricately curled around it. As they dry these
bands expand, and are seen to be four lines at right angles, Avith
the ends clubbed, as it may be called. If, whilst watching them,
the spores are breathed upon, these bands immediately return to
their former state, and are closely curled around the spore ; but
as they gradually dry again expand. This experiment may be
repeated several times, and is a very interesting one.

The above are the principal objects which could not possibly be

OF MICROSCOPIC OBJECTS. 137

included in any of the former chapters, but would have left a
most interesting branch untouched had it been neglected. There
is another subject also which should not be passed by — viz., the
production of minute pictures which serve as objects for microscopic
examination. I may here mention that as this manual is simply
to enable the young student to prepare and mount his objects,
the photography of magnified objects has evidently no place here.

Few slides caused so much astonishment as these minute
photographs when first exhibited ; small spots were seen to con-
tain large pictures, and a page of printed matter was compressed
into the one-hundredth part of a square inch. It would be im-
possible in this place to give the inquirer any instruction in the
manipulation of photography, so it must be assumed that he al-
ready knows this.

We will first consider the process performed by artificial light.
The collodion employed in photographing generally shows as
much structure when magnified as is found in linen of moderate
texture; but this is not always the case, as some samples bear
much enlargement without any of this appearance. It is evident
that a structure so coarse would make it entirely unfit for these
minute pictures, as all the small markings would be destroyed, or
so interfered with that no great enlargement would be practicable.
To obtain almost structureless collodion is not an easy matter, and
a clever practitioner in this branch of photography states that he
knows of no method to accomplish this with certainty, but he
himself tries different samples until he falls upon a suitable one,
which he then lays aside for this object. A beneficial effect is
often derived from keeping the collodion awhile, but this is not
always the case. The slides should be chosen of an equal thick-
ness, so that when focussed upon one no re-adjustment may be
necessary for the others. The glass should, of course, be free
from any roughness, scratches, or other imperfections, and of first-
rate quality and colour.

The microscope must then be placed in a horizontal position,
and the eye-piece removed, the stage having a small clip upon it
to keep the prepared plate in position. The negative must then
be supported at a distance from the end of the microscope tube
from which the eye-piece was withdrawn. The distance will, of

138 PREPARATION AND MOUNTING

course, vary according to the relative sizes of the negative and
desired picture. With a one-inch object glass, which is a very
convenient focus, it will have to be changed usually betwixt one
and four feet. The negative must be lighted by an argand gas-
burner or camphene-lamp, and the rays rendered as parallel as
possible by the use of a large lens placed betwixt the light and the
negative. It is not easy to arrange the apparatus so as to get the
light uniform ; but a little practice will soon do away with this
difficulty. Ordinary ground-glass is too coarsely grained to focus
upon, as the magnifying power used to examine the minute re-
flection must be considerable. One of the slides must therefore
be coated with the collodion, submitted to the silver-bath, and
after washing with water be allowed to dry. Upon this may be
focussed the reflected image, and its minuteness examined with a
powerful hand-magnifier, or another microscope placed behind in
a horizontal position. When the utmost sharpness of definition
is obtained, it is usually required to remove the plate a little dis-
tance from the object-glass, as object-glasses for the microscope
are slightly " over corrected," and the chemical rays which ac-
complish the photography are beyond the visual ones. The exact
distance required to give a picture to bear the greatest enlarge-
ment cannot be given by rule ; but experiments must be made at
first, and it will always be the same with the object-glass which we
have tested.

The plate may now be prepared as in ordinary photography,
and placed upon the stage whilst the light is shaded. When all
is ready, the shade is removed and the process allowed to go on,
usually for thirty or forty seconds; but no certain rule can be
given as to the required time, on account of various collodions,
lamps, and powers being used. It may be here mentioned, that
it is well to contrive some little frame to receive the prepared
plate, as the silver bath solution is liable to get upon the micro-
scope stage and so, to say the least, disfigure it. When the ex-
posure has been continued sufficiently long, the pkture may be
developed by any of the ordinary methods, but some of the best
productions have been brought out by the aid of pyrogallic and
citric acid solution, with the addition of a little alcohol. The
" fixing " may be effected by a strong solution of hyposulphite of

OF MICROSCOPIC OBJECTS. 139

soda, and the picture must then be very well washed with pure
water. When dry, the photograph must be mounted with
Canada balsam, in the same manner as any ordinary object ; but
great heat must not be used, or the picture may be injured.

When ordinary daylight is employed for this purpose, a dark
slide will be required for the prepared plate, in the same way as
for photographing landscape, &c. These dark slides are generally
made by each individual to suit his particular arrangements of
negatives, &c. ; but it may be here recommended that the opera-
tor should always focus in the same slide which he is about to
use, as so small a difference in distance lies betwixt perfection and
failure.

For an ordinary student, perhaps the above method is that which
is the most readily used, and consequently the most generally
available ; but almost every one has a different arrangement of
microscope, &c., by which he procures these minute pictures.
Mr. Shadbolt (one of our most successful photographers) gives the
following instructions : — " Having removed the upper stage plate
of a large compound microscope, I replace it with one of wood,
supplied with guide pins of silver wire, in order to admit of its
supporting a slip of glass coated with collodion, and excited in the
' nitrate of silver bath in the usual way. If the ordinary brass stage
plate were left undisturbed, it is obvious that it and the excited
slip of glass would be mutually destructive.

" The microscope is now to be placed in a horizontal position,
the objective, intended to produce the picture, made to occupy
the place usually filled by the achromatic condenser on the sub-
stage of the microscope, while another objective is screwed into
the lower end of the body of the instrument, which is used not
only to focus with, but also to make the requisite allowance for
actinic variation.

" The negative intended to be reduced is then arranged verti-
cally, with its centre in the axis of the microscopic body, at a dis-
tance of from two to four feet from the lower object-glass, and
with a convenient screen of card, wood, or thick paper, to cut off
any extraneous light that would otherwise pass beyond the limits
of the picture.

" A small camphene-lamp is employed for the purpose of illumi-

140 PREPARATION AND MOUNTING OP MICROSCOPIC OBJECTS.

nating the negative, having a good bull's-eye lens as a condenser,
so arranged with its flat side next the lamp that the refracted rays
shall just fill the whole of a double convex lens of about six inches
in diameter, the latter being placed in such a position as to refract
the rays of light in a parallel direction upon the negative. By
this arrangement the bulVs-eye lens of about two inches and a half-
in diameter appears as the source of the light instead of the small
flame of the lamp.

" By using a bat's- wing gas-burner of a good size, a single lens,
instead of the two, may be so placed as to give the necessary
uniformity of illumination."

This arrangement requires the same care in working as that
before mentioned, the picture being produced, developed, and fixed
by the same treatment.

As before stated, almost every manipulator makes some small
changes in the method of producing these minute pictures ; but
the rules given, though far from new, are sufficient for all purposes ;
and I may state with truth, that those which I procured when
these wonders were quite new, are fully equal in every respect to
the best usually met with at the present time.

With these instructions I shall close my Handbook, as I believe
that every branch of Preparation and Mounting of Microscopic
Objects has been treated of. Not that the beginner can expect
that he has nothing to do except read this to be able to mount
everything ; but there are difficulties from which he may be freed
by instruction, when otherwise he would have been compelled to
learn by failure alone. I may, here, however, repeat certain ad-
vice before given, — that, when practicable, it is a good thing to
mount each object by two or more different methods, as very fre-
quently one feature is best shown dry, another in liquid, and a
third in balsam. Secondly, let the mounting be studied thorough-
ly, as no part of the microscopic science is more worthy of thought
than this. And lastly, let no failures prevent you following up
what will assuredly one day become a source of great pleasure,
and render your daily " constitutional walk," which is often dull
in the extreme, very delightful, as it will afford you some new
wonder in every hedge-row.

INDEX.

AIR-BUBBLES, 57.

Air-pump, 19; use of, 58.

Alcock, Dr., on tongues of Mollusca,
111.

Algse, mounting of, 88.

Anacharis alsinastrum, rotation in,
134; to cultivate, 135.

Animal tissues, dissection of, 108.

Antenna of insects, 70; in preserva-
tive liquid, 91.

Apparatus required in mounting ob-
jects, 1.

Arteries, how to distinguish, in injec-
tion, 123.

Asparagus, spiral vessels of, 108.

Asphaltum, 21; and india-rubber, as
cement and varnish, 24.

BAT, circulation of blood in win 0-3 of
133.

Beale's, Dr., Prussian blue for inject-
ing, 125 ; carmine, 126.

Bell-glasses, use of, 19.

Berg-mehl, 43.

Bermuda earth, 43,

Bichromate of lead, injection with,
124.

Bird, Dr. Golding, on preparation of
Zoophytes, 65.

Black-japan, as a cement, 22.

Black varnish, 23.

Blood, as a microscopic object, 52 ;
circulation of, 131-140.

Bone, sections of, 97 ; fossil, 99.

Brass plate for heating glasses, &c., 19.

CACTACE.E, raphides of, 54.
Camel-hair pencils, use of, 17.

Canada balsam, 20 ; with chloroform,
20, 61, 124; with turpentine, 21;
air-bubbles in, 57 ; Dr. Carpenter's
syringe for, 59 ; to fill cells with,
ib. ; mounting of objects in, 57.

Carbonic acid, 83.

Carmine injecting fluid, Dr. Beale's,
125; Dale & Davies', 129.

Cartilage, dissection of, 108.

Castor oil, as a preservative, 83.

Cells for dry objects, 13; with rings
of cardboard, 15; with gutta-percha,
14 ; with leather, ib. ; with ivory,
15; with thin glass, 14 ; with var-
nish, 28, 31; for balsam, 59; for
preservative liquids, 84-87 ; Shad-
bolt's turntable useful in making, 16.

Cements, 20-23.

Chalk, foraminifera from, 63.

Chara vulgaris, rotation in, 134.

Chloride of zinc, solution of, 83; of
calcium, solution of, 89.

Chloroform, use of (see Canada bal-
sam).

Circulation of blood, 131-133 ; of sap
(see Rotation).

Cleanliness in microscopic work, 9.

Coal, sections of, 95.

Collection of diatoms, 33.

Colours for injection, 117-119.

Condenser, cheap, to make, 26.

Corals, sections of, 95.

Corallines, to mount, 50.

Cover of objects, to remove, 61.

Crystals, mounting of, dry, 52 ; to
vary form of, and mount in balsam,
73; sections of, 104

Cuticle of equisetum, &c., 79.

142

INDEX.

DALE & DAVIES', carmine injection, 129.

Deane's gelatine, 82.

Decalcifying process for shells, 94.

Desmidiacese, in preservative liquid, 89.

Diachaea elegans, 54.

Diamond beetle, 55.

Diatomacea?, nature of, 32 ; collection
of, 33 ; in stomachs of fish, 84; to
prepare and mount dry, 34-43 ; Mr.
Ry lands on, 37; in guano, 42 ; fos-
silized, 43 ; mounting in balsam, 61 ;
mounting in preservative liquids, 89.

Discs used in mounting, 27 ; support-
er, Smith & Beck's, 28.

Dissection, 105; microscope for, ib. ;
instruments for, 106.

Distilled water, as preservative liquid,
81.

Doyer's, M., method of injection, 124.

Dry objects, to mount, 27.

ECHINODERMATA SPINES, Sections of,

94.

Eel, scales of, 76.

Eggs of insects, 91.

Elastic objects, to keep flat upon the
slide, 18.

Electrical cement, 22.

Equisetaceaj, 79; spores of, 136.

Erector, not indispensable, 25.

Eyes of insects, 69, 66; of animals in-
jected, 128.

FEATHERS, 72.

Feet of insects, 55, 71.

Ferns, 52 ; development of spores of,
135.

Fish, fins and tails of, 52 ; scales of,
55, 77; injection of, 128; circula-
tion of blood in, 132.

Flint, sections of, 96.

Fluid, mounting objects in, 81.

Flustra avicularis, 77.

Fly (sec Insects).

Foot of sheep injected, 128.

Foraminifera, 44 ; separation of, ib. ;
to clean, ib. ; to clean from tallow
soundings, 45 ; to mount, 47, 63 ;
from chalk, 63.

Forceps, ordinary and wooden, 18;
bull-nosed, for injection, 116.

Fossil infusoria, 43.

Frog, injected, 128; to show circula-
tion of blood, 131.

Frog-bit, rotation in, 134.
Fruit- stones, sections of, 99.
Fungi, 54, 90.

GASTRIC teeth of insects, 113; of mol-
luscs, 111.

Gelatine for injection, 117 ; preserva-
tive liquid, 82.

Glass slides, 9 ; thin, 10 ; thin, to cut,
11; thin, to measure, 12; thin, to
clean, ib. ; cells, to make, 85 ; rings
for cells, 86 ; tubes, 17.

Glycerine. 82, 91 ; jelly, 82, 88.

Goadby's fluid, 83.

Gold-size, 22.

Grasses, 79.

Grasshopper, gizzard of, 113.

Guano, containing Diatomaceas, 42.

Gum-water, and modifications of, 23.

Gutta-percha cells, 14; for liquids, 85.

HAIRS, vegetable, 49 ; to mount dry,
56 ; to mount as polarizing objects,
77 ; sections of, 100.

Hepworth, Mr., on mounting insects,
68.

Horn, sections of, 99.

Hot-water bath, use of, 59.

INFUSORIA, in preservative liquid, 89 ;
fossil, 43.

Injections, 115; apparatus for, ib. ;
colours for, 117 ; directions for, 120;
with various colours, 123 ; mount-
ing of, ib. ; transparent, 125, 129.

Insects, scales of, 50; to mount, 51;
legs and feet of, 55, 71 : eyes of, 56,
69 ; Mr. Hepworth on mounting,
68; antennae of, 70; mouth of, 71;
trachea! and spiracles of, 72, 109;
parasitic, 72; in preservative liquid,
91; eggs of, ib. ; gizzard of, 113;
circulation of blood in, 133.

Intestines, injected, 128.

KNIVES for dissecting, 106; Valen-
tin's, 102.

LABELLING of objects, 25.

Lamps, for mounting, 19.

Larvse, skins of, 52.

Leaves, sections of, 102 ; scales of, 49,

79.

Liquid-glue, 22.
Lungs of animals injected, 128.

INDEX.

143

MALLOW, pollen of, 49.

Marine glue, 21.

Microscope for dissection, 105.

Miscellaneous, 131.

Mites, 72.

Molluscs, tongues of, 110.

Mosses, 53 ; in preservative fluids, 88.

Mould (see .Fungi).

Mounting objects, apparatus for, 9;

dry, 27 ; in Canada balsam, 57 ; in

cells, 81.
Mouse, ear of, 108 ; circulation of blood

in, 133.

Mouth of insects, 71.
Muscle, dissection of, 108.

NEEDLES, how to mount, 17 ; for dis-
section, 106; curved, for injection,
116.

Nervous tissue, dissection of, 109.

Nettle leaf, 53.

Newts, injected, 128.

ONION, raphides of, 54.

Orbitolite, section of, 93.

Oxalurate of ammonia, crystals of, 74.

PALATES of Molluscs (see Tongues).

Papers, ornamental, to cover slides,
15, 31.

Photographs, microscopic, to produce,
137 ; Mr. Shadbolt on, 139.

Pipes for injecting syringe, 115.

Podura, scales of, 51.

Polariscope, objects for, 73-80, 99.

Pollen, 49, 73.

Polycystinffi, preparation and mount-
ing of, 63.

Preservative liquids, 81 ; cells suited
for, 84. 88.

Prussian blue for injection, 125.

RAPHIDES, vegetable, 54, 78.
Rhinoceros, horn of, 99.
Rhubarb, spiral vessels of, 107.
Rings and cross of crystals, 104.
Rotation of fluid in cells of plants, 133

-135.

Rush, section of, 102.
Rylands, Mr. T. G., on Diatomacese,

37, 90.

SALICIXE, crystals of, 74.
Saw of watch-spring, 93.

Scales of fishes, 55, 76; of leaves, 49,
79 ; of insects, 50.

Scissors, 1 7 ; for dissection, 106. ~

Sea mats, 55.

Sea-soundings, to cleanse, 45.

Sealing wax varnish, 23.

Sections, 92 ; of shells, 93 ; of orbito-
lite, ib. ; of spines of Echinoderma-
ta, 94 ; of corals, 95 ; of coal, ib. ;
of flint, 96; of teeth, ib. ; of bone,
97 ; of fruit-stones, 99 ; of horn, ib. ;
of whalebone, 100; of hairs, ib. ;
of wood, ib. ; of leaves, 102; of
sponges, 103; of skin, ib. ; of crys-
tals, 104; of seeds, 105.

Seeds, 50, 73 ; sections of, 105 ; growth
of, 135.

Shadbolt's turntable, 1 6.

Shells, sections of, 92; decalcifying,
94 ; laminae of, ib.

Siliceous cuticles, 79.

Size for injection, 117.

Skins of larva?, 52 ; sections of, 103 ;
sole, 55.

Slides, glass, for mounting objects, 9 ;
glass, to clean, 10; wood, &c., 14;
most useful, 15 ; to cover and var-
nish, 32.

Spicula, from sponges, &c., 67.

Spines of Echinus, 94.

Spiracles of insects, 72, 110.

Spiral vessels of vegetables, 107.

Split bristles, use of, 17.

Sponges, sections of, 103.

Spores of ferns, development of, 135 ;
equisetum, 136.

Starch, preparation and mounting of,
78.

Sulphate of copper and magnesia,
crystals of, 75.

Syringe for Canada balsam, 59 ; for
dissection, 107; for injection, 115.

TADPOLE, to show circulation of blood

of, 132.

Teeth, sect ions of, 96.
Thin glass, to cut, 11 ; to measure

thickness of, 12 ; to clean, ib.
Thwaites' preservative liquid, 83.
Ticks, 72.
Tissues, animal and vegetable (see

Dissection).
Tongues or palates of Molluscs, 110.

144

INDEX.

Tracheae of insects, 71, 109.
Transfer of objects, 17.
Trough for dissection, 107.
Tubes, glass, 17.

Turnbull's, Dr., Prussian blue for in-
jection, 126.
Turpentine, use of, 58.

UNIVERSAL STAND, to make, 25.

VALENTIN'S KNIFE, 102.
Vallisneria spiralis, rotation in, 134;
to cultivate, 135.

Tarnishes, 23.

Vegetable objects, to mount dry, 48 ;

to mount in jelly, 88 ; dissection of,

107.

WATCH-GLASSES, 19.
Whalebone, sections of, 100.
Wood, sections of, ib.

ZOOPHYTES, to mount dry, 55 ; Dr.
Golding Bird on mounting, in bal-
sam, 65 ; as polarizing objects, 77.

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